    /* png.h - header file for PNG reference library
     *
     * libpng version 1.6.7 - November 14, 2013
     * Copyright (c) 1998-2013 Glenn Randers-Pehrson
     * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
     * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
     *
     * This code is released under the libpng license (See LICENSE, below)
     *
     * Authors and maintainers:
     *   libpng versions 0.71, May 1995, through 0.88, January 1996: Guy Schalnat
     *   libpng versions 0.89c, June 1996, through 0.96, May 1997: Andreas Dilger
     *   libpng versions 0.97, January 1998, through 1.6.7 - November 14, 2013: Glenn
     *   See also "Contributing Authors", below.
     *
     * Note about libpng version numbers:
     *
     *   Due to various miscommunications, unforeseen code incompatibilities
     *   and occasional factors outside the authors' control, version numbering
     *   on the library has not always been consistent and straightforward.
     *   The following table summarizes matters since version 0.89c, which was
     *   the first widely used release:
     *
     *    source                 png.h  png.h  shared-lib
     *    version                string   int  version
     *    -------                ------ -----  ----------
     *    0.89c "1.0 beta 3"     0.89      89  1.0.89
     *    0.90  "1.0 beta 4"     0.90      90  0.90  [should have been 2.0.90]
     *    0.95  "1.0 beta 5"     0.95      95  0.95  [should have been 2.0.95]
     *    0.96  "1.0 beta 6"     0.96      96  0.96  [should have been 2.0.96]
     *    0.97b "1.00.97 beta 7" 1.00.97   97  1.0.1 [should have been 2.0.97]
     *    0.97c                  0.97      97  2.0.97
     *    0.98                   0.98      98  2.0.98
     *    0.99                   0.99      98  2.0.99
     *    0.99a-m                0.99      99  2.0.99
     *    1.00                   1.00     100  2.1.0 [100 should be 10000]
     *    1.0.0      (from here on, the   100  2.1.0 [100 should be 10000]
     *    1.0.1       png.h string is   10001  2.1.0
     *    1.0.1a-e    identical to the  10002  from here on, the shared library
     *    1.0.2       source version)   10002  is 2.V where V is the source code
     *    1.0.2a-b                      10003  version, except as noted.
     *    1.0.3                         10003
     *    1.0.3a-d                      10004
     *    1.0.4                         10004
     *    1.0.4a-f                      10005
     *    1.0.5 (+ 2 patches)           10005
     *    1.0.5a-d                      10006
     *    1.0.5e-r                      10100 (not source compatible)
     *    1.0.5s-v                      10006 (not binary compatible)
     *    1.0.6 (+ 3 patches)           10006 (still binary incompatible)
     *    1.0.6d-f                      10007 (still binary incompatible)
     *    1.0.6g                        10007
     *    1.0.6h                        10007  10.6h (testing xy.z so-numbering)
     *    1.0.6i                        10007  10.6i
     *    1.0.6j                        10007  2.1.0.6j (incompatible with 1.0.0)
     *    1.0.7beta11-14        DLLNUM  10007  2.1.0.7beta11-14 (binary compatible)
     *    1.0.7beta15-18           1    10007  2.1.0.7beta15-18 (binary compatible)
     *    1.0.7rc1-2               1    10007  2.1.0.7rc1-2 (binary compatible)
     *    1.0.7                    1    10007  (still compatible)
     *    1.0.8beta1-4             1    10008  2.1.0.8beta1-4
     *    1.0.8rc1                 1    10008  2.1.0.8rc1
     *    1.0.8                    1    10008  2.1.0.8
     *    1.0.9beta1-6             1    10009  2.1.0.9beta1-6
     *    1.0.9rc1                 1    10009  2.1.0.9rc1
     *    1.0.9beta7-10            1    10009  2.1.0.9beta7-10
     *    1.0.9rc2                 1    10009  2.1.0.9rc2
     *    1.0.9                    1    10009  2.1.0.9
     *    1.0.10beta1              1    10010  2.1.0.10beta1
     *    1.0.10rc1                1    10010  2.1.0.10rc1
     *    1.0.10                   1    10010  2.1.0.10
     *    1.0.11beta1-3            1    10011  2.1.0.11beta1-3
     *    1.0.11rc1                1    10011  2.1.0.11rc1
     *    1.0.11                   1    10011  2.1.0.11
     *    1.0.12beta1-2            2    10012  2.1.0.12beta1-2
     *    1.0.12rc1                2    10012  2.1.0.12rc1
     *    1.0.12                   2    10012  2.1.0.12
     *    1.1.0a-f                 -    10100  2.1.1.0a-f (branch abandoned)
     *    1.2.0beta1-2             2    10200  2.1.2.0beta1-2
     *    1.2.0beta3-5             3    10200  3.1.2.0beta3-5
     *    1.2.0rc1                 3    10200  3.1.2.0rc1
     *    1.2.0                    3    10200  3.1.2.0
     *    1.2.1beta1-4             3    10201  3.1.2.1beta1-4
     *    1.2.1rc1-2               3    10201  3.1.2.1rc1-2
     *    1.2.1                    3    10201  3.1.2.1
     *    1.2.2beta1-6            12    10202  12.so.0.1.2.2beta1-6
     *    1.0.13beta1             10    10013  10.so.0.1.0.13beta1
     *    1.0.13rc1               10    10013  10.so.0.1.0.13rc1
     *    1.2.2rc1                12    10202  12.so.0.1.2.2rc1
     *    1.0.13                  10    10013  10.so.0.1.0.13
     *    1.2.2                   12    10202  12.so.0.1.2.2
     *    1.2.3rc1-6              12    10203  12.so.0.1.2.3rc1-6
     *    1.2.3                   12    10203  12.so.0.1.2.3
     *    1.2.4beta1-3            13    10204  12.so.0.1.2.4beta1-3
     *    1.0.14rc1               13    10014  10.so.0.1.0.14rc1
     *    1.2.4rc1                13    10204  12.so.0.1.2.4rc1
     *    1.0.14                  10    10014  10.so.0.1.0.14
     *    1.2.4                   13    10204  12.so.0.1.2.4
     *    1.2.5beta1-2            13    10205  12.so.0.1.2.5beta1-2
     *    1.0.15rc1-3             10    10015  10.so.0.1.0.15rc1-3
     *    1.2.5rc1-3              13    10205  12.so.0.1.2.5rc1-3
     *    1.0.15                  10    10015  10.so.0.1.0.15
     *    1.2.5                   13    10205  12.so.0.1.2.5
     *    1.2.6beta1-4            13    10206  12.so.0.1.2.6beta1-4
     *    1.0.16                  10    10016  10.so.0.1.0.16
     *    1.2.6                   13    10206  12.so.0.1.2.6
     *    1.2.7beta1-2            13    10207  12.so.0.1.2.7beta1-2
     *    1.0.17rc1               10    10017  12.so.0.1.0.17rc1
     *    1.2.7rc1                13    10207  12.so.0.1.2.7rc1
     *    1.0.17                  10    10017  12.so.0.1.0.17
     *    1.2.7                   13    10207  12.so.0.1.2.7
     *    1.2.8beta1-5            13    10208  12.so.0.1.2.8beta1-5
     *    1.0.18rc1-5             10    10018  12.so.0.1.0.18rc1-5
     *    1.2.8rc1-5              13    10208  12.so.0.1.2.8rc1-5
     *    1.0.18                  10    10018  12.so.0.1.0.18
     *    1.2.8                   13    10208  12.so.0.1.2.8
     *    1.2.9beta1-3            13    10209  12.so.0.1.2.9beta1-3
     *    1.2.9beta4-11           13    10209  12.so.0.9[.0]
     *    1.2.9rc1                13    10209  12.so.0.9[.0]
     *    1.2.9                   13    10209  12.so.0.9[.0]
     *    1.2.10beta1-7           13    10210  12.so.0.10[.0]
     *    1.2.10rc1-2             13    10210  12.so.0.10[.0]
     *    1.2.10                  13    10210  12.so.0.10[.0]
     *    1.4.0beta1-5            14    10400  14.so.0.0[.0]
     *    1.2.11beta1-4           13    10211  12.so.0.11[.0]
     *    1.4.0beta7-8            14    10400  14.so.0.0[.0]
     *    1.2.11                  13    10211  12.so.0.11[.0]
     *    1.2.12                  13    10212  12.so.0.12[.0]
     *    1.4.0beta9-14           14    10400  14.so.0.0[.0]
     *    1.2.13                  13    10213  12.so.0.13[.0]
     *    1.4.0beta15-36          14    10400  14.so.0.0[.0]
     *    1.4.0beta37-87          14    10400  14.so.14.0[.0]
     *    1.4.0rc01               14    10400  14.so.14.0[.0]
     *    1.4.0beta88-109         14    10400  14.so.14.0[.0]
     *    1.4.0rc02-08            14    10400  14.so.14.0[.0]
     *    1.4.0                   14    10400  14.so.14.0[.0]
     *    1.4.1beta01-03          14    10401  14.so.14.1[.0]
     *    1.4.1rc01               14    10401  14.so.14.1[.0]
     *    1.4.1beta04-12          14    10401  14.so.14.1[.0]
     *    1.4.1                   14    10401  14.so.14.1[.0]
     *    1.4.2                   14    10402  14.so.14.2[.0]
     *    1.4.3                   14    10403  14.so.14.3[.0]
     *    1.4.4                   14    10404  14.so.14.4[.0]
     *    1.5.0beta01-58          15    10500  15.so.15.0[.0]
     *    1.5.0rc01-07            15    10500  15.so.15.0[.0]
     *    1.5.0                   15    10500  15.so.15.0[.0]
     *    1.5.1beta01-11          15    10501  15.so.15.1[.0]
     *    1.5.1rc01-02            15    10501  15.so.15.1[.0]
     *    1.5.1                   15    10501  15.so.15.1[.0]
     *    1.5.2beta01-03          15    10502  15.so.15.2[.0]
     *    1.5.2rc01-03            15    10502  15.so.15.2[.0]
     *    1.5.2                   15    10502  15.so.15.2[.0]
     *    1.5.3beta01-10          15    10503  15.so.15.3[.0]
     *    1.5.3rc01-02            15    10503  15.so.15.3[.0]
     *    1.5.3beta11             15    10503  15.so.15.3[.0]
     *    1.5.3 [omitted]
     *    1.5.4beta01-08          15    10504  15.so.15.4[.0]
     *    1.5.4rc01               15    10504  15.so.15.4[.0]
     *    1.5.4                   15    10504  15.so.15.4[.0]
     *    1.5.5beta01-08          15    10505  15.so.15.5[.0]
     *    1.5.5rc01               15    10505  15.so.15.5[.0]
     *    1.5.5                   15    10505  15.so.15.5[.0]
     *    1.5.6beta01-07          15    10506  15.so.15.6[.0]
     *    1.5.6rc01-03            15    10506  15.so.15.6[.0]
     *    1.5.6                   15    10506  15.so.15.6[.0]
     *    1.5.7beta01-05          15    10507  15.so.15.7[.0]
     *    1.5.7rc01-03            15    10507  15.so.15.7[.0]
     *    1.5.7                   15    10507  15.so.15.7[.0]
     *    1.6.0beta01-40          16    10600  16.so.16.0[.0]
     *    1.6.0rc01-08            16    10600  16.so.16.0[.0]
     *    1.6.0                   16    10600  16.so.16.0[.0]
     *    1.6.1beta01-09          16    10601  16.so.16.1[.0]
     *    1.6.1rc01               16    10601  16.so.16.1[.0]
     *    1.6.1                   16    10601  16.so.16.1[.0]
     *    1.6.2beta01             16    10602  16.so.16.2[.0]
     *    1.6.2rc01-06            16    10602  16.so.16.2[.0]
     *    1.6.2                   16    10602  16.so.16.2[.0]
     *    1.6.3beta01-11          16    10603  16.so.16.3[.0]
     *    1.6.3rc01               16    10603  16.so.16.3[.0]
     *    1.6.3                   16    10603  16.so.16.3[.0]
     *    1.6.4beta01-02          16    10604  16.so.16.4[.0]
     *    1.6.4rc01               16    10604  16.so.16.4[.0]
     *    1.6.4                   16    10604  16.so.16.4[.0]
     *    1.6.5                   16    10605  16.so.16.5[.0]
     *    1.6.6                   16    10606  16.so.16.6[.0]
     *    1.6.7beta01-04          16    10607  16.so.16.7[.0]
     *    1.6.7rc01-02            16    10607  16.so.16.7[.0]
     *    1.6.7                   16    10607  16.so.16.7[.0]
     *
     *   Henceforth the source version will match the shared-library major
     *   and minor numbers; the shared-library major version number will be
     *   used for changes in backward compatibility, as it is intended.  The
     *   PNG_LIBPNG_VER macro, which is not used within libpng but is available
     *   for applications, is an unsigned integer of the form xyyzz corresponding
     *   to the source version x.y.z (leading zeros in y and z).  Beta versions
     *   were given the previous public release number plus a letter, until
     *   version 1.0.6j; from then on they were given the upcoming public
     *   release number plus "betaNN" or "rcNN".
     *
     *   Binary incompatibility exists only when applications make direct access
     *   to the info_ptr or png_ptr members through png.h, and the compiled
     *   application is loaded with a different version of the library.
     *
     *   DLLNUM will change each time there are forward or backward changes
     *   in binary compatibility (e.g., when a new feature is added).
     *
     * See libpng-manual.txt or libpng.3 for more information.  The PNG
     * specification is available as a W3C Recommendation and as an ISO
     * Specification, <http://www.w3.org/TR/2003/REC-PNG-20031110/
     */

    /*
     * COPYRIGHT NOTICE, DISCLAIMER, and LICENSE:
     *
     * If you modify libpng you may insert additional notices immediately following
     * this sentence.
     *
     * This code is released under the libpng license.
     *
     * libpng versions 1.2.6, August 15, 2004, through 1.6.7, November 14, 2013, are
     * Copyright (c) 2004, 2006-2013 Glenn Randers-Pehrson, and are
     * distributed according to the same disclaimer and license as libpng-1.2.5
     * with the following individual added to the list of Contributing Authors:
     *
     *    Cosmin Truta
     *
     * libpng versions 1.0.7, July 1, 2000, through 1.2.5, October 3, 2002, are
     * Copyright (c) 2000-2002 Glenn Randers-Pehrson, and are
     * distributed according to the same disclaimer and license as libpng-1.0.6
     * with the following individuals added to the list of Contributing Authors:
     *
     *    Simon-Pierre Cadieux
     *    Eric S. Raymond
     *    Gilles Vollant
     *
     * and with the following additions to the disclaimer:
     *
     *    There is no warranty against interference with your enjoyment of the
     *    library or against infringement.  There is no warranty that our
     *    efforts or the library will fulfill any of your particular purposes
     *    or needs.  This library is provided with all faults, and the entire
     *    risk of satisfactory quality, performance, accuracy, and effort is with
     *    the user.
     *
     * libpng versions 0.97, January 1998, through 1.0.6, March 20, 2000, are
     * Copyright (c) 1998, 1999, 2000 Glenn Randers-Pehrson, and are
     * distributed according to the same disclaimer and license as libpng-0.96,
     * with the following individuals added to the list of Contributing Authors:
     *
     *    Tom Lane
     *    Glenn Randers-Pehrson
     *    Willem van Schaik
     *
     * libpng versions 0.89, June 1996, through 0.96, May 1997, are
     * Copyright (c) 1996, 1997 Andreas Dilger
     * Distributed according to the same disclaimer and license as libpng-0.88,
     * with the following individuals added to the list of Contributing Authors:
     *
     *    John Bowler
     *    Kevin Bracey
     *    Sam Bushell
     *    Magnus Holmgren
     *    Greg Roelofs
     *    Tom Tanner
     *
     * libpng versions 0.5, May 1995, through 0.88, January 1996, are
     * Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
     *
     * For the purposes of this copyright and license, "Contributing Authors"
     * is defined as the following set of individuals:
     *
     *    Andreas Dilger
     *    Dave Martindale
     *    Guy Eric Schalnat
     *    Paul Schmidt
     *    Tim Wegner
     *
     * The PNG Reference Library is supplied "AS IS".  The Contributing Authors
     * and Group 42, Inc. disclaim all warranties, expressed or implied,
     * including, without limitation, the warranties of merchantability and of
     * fitness for any purpose.  The Contributing Authors and Group 42, Inc.
     * assume no liability for direct, indirect, incidental, special, exemplary,
     * or consequential damages, which may result from the use of the PNG
     * Reference Library, even if advised of the possibility of such damage.
     *
     * Permission is hereby granted to use, copy, modify, and distribute this
     * source code, or portions hereof, for any purpose, without fee, subject
     * to the following restrictions:
     *
     *   1. The origin of this source code must not be misrepresented.
     *
     *   2. Altered versions must be plainly marked as such and must not
     *      be misrepresented as being the original source.
     *
     *   3. This Copyright notice may not be removed or altered from
     *      any source or altered source distribution.
     *
     * The Contributing Authors and Group 42, Inc. specifically permit, without
     * fee, and encourage the use of this source code as a component to
     * supporting the PNG file format in commercial products.  If you use this
     * source code in a product, acknowledgment is not required but would be
     * appreciated.
     */

    /*
     * A "png_get_copyright" function is available, for convenient use in "about"
     * boxes and the like:
     *
     *     printf("%s", png_get_copyright(NULL));
     *
     * Also, the PNG logo (in PNG format, of course) is supplied in the
     * files "pngbar.png" and "pngbar.jpg (88x31) and "pngnow.png" (98x31).
     */

    /*
     * Libpng is OSI Certified Open Source Software.  OSI Certified is a
     * certification mark of the Open Source Initiative.
     */

    /*
     * The contributing authors would like to thank all those who helped
     * with testing, bug fixes, and patience.  This wouldn't have been
     * possible without all of you.
     *
     * Thanks to Frank J. T. Wojcik for helping with the documentation.
     */

    /*
     * Y2K compliance in libpng:
     * =========================
     *
     *    November 14, 2013
     *
     *    Since the PNG Development group is an ad-hoc body, we can't make
     *    an official declaration.
     *
     *    This is your unofficial assurance that libpng from version 0.71 and
     *    upward through 1.6.7 are Y2K compliant.  It is my belief that
     *    earlier versions were also Y2K compliant.
     *
     *    Libpng only has two year fields.  One is a 2-byte unsigned integer
     *    that will hold years up to 65535.  The other, which is deprecated,
     *    holds the date in text format, and will hold years up to 9999.
     *
     *    The integer is
     *        "png_uint_16 year" in png_time_struct.
     *
     *    The string is
     *        "char time_buffer[29]" in png_struct.  This is no longer used
     *    in libpng-1.6.x and will be removed from libpng-1.7.0.
     *
     *    There are seven time-related functions:
     *        png.c: png_convert_to_rfc_1123_buffer() in png.c
     *          (formerly png_convert_to_rfc_1123() prior to libpng-1.5.x and
     *          png_convert_to_rfc_1152() in error prior to libpng-0.98)
     *        png_convert_from_struct_tm() in pngwrite.c, called in pngwrite.c
     *        png_convert_from_time_t() in pngwrite.c
     *        png_get_tIME() in pngget.c
     *        png_handle_tIME() in pngrutil.c, called in pngread.c
     *        png_set_tIME() in pngset.c
     *        png_write_tIME() in pngwutil.c, called in pngwrite.c
     *
     *    All handle dates properly in a Y2K environment.  The
     *    png_convert_from_time_t() function calls gmtime() to convert from system
     *    clock time, which returns (year - 1900), which we properly convert to
     *    the full 4-digit year.  There is a possibility that libpng applications
     *    are not passing 4-digit years into the png_convert_to_rfc_1123_buffer()
     *    function, or that they are incorrectly passing only a 2-digit year
     *    instead of "year - 1900" into the png_convert_from_struct_tm() function,
     *    but this is not under our control.  The libpng documentation has always
     *    stated that it works with 4-digit years, and the APIs have been
     *    documented as such.
     *
     *    The tIME chunk itself is also Y2K compliant.  It uses a 2-byte unsigned
     *    integer to hold the year, and can hold years as large as 65535.
     *
     *    zlib, upon which libpng depends, is also Y2K compliant.  It contains
     *    no date-related code.
     *
     *       Glenn Randers-Pehrson
     *       libpng maintainer
     *       PNG Development Group
     */

    #ifndef PNG_H
    #define PNG_H

    /* This is not the place to learn how to use libpng. The file libpng-manual.txt
     * describes how to use libpng, and the file example.c summarizes it
     * with some code on which to build.  This file is useful for looking
     * at the actual function definitions and structure components.
     *
     * If you just need to read a PNG file and don't want to read the documentation
     * skip to the end of this file and read the section entitled 'simplified API'.
     */

    /* Version information for png.h - this should match the version in png.c */
    #define PNG_LIBPNG_VER_STRING "1.6.7"
    #define PNG_HEADER_VERSION_STRING \
         " libpng version 1.6.7 - November 14, 2013\n"

    #define PNG_LIBPNG_VER_SONUM   16
    #define PNG_LIBPNG_VER_DLLNUM  16

    /* These should match the first 3 components of PNG_LIBPNG_VER_STRING: */
    #define PNG_LIBPNG_VER_MAJOR   1
    #define PNG_LIBPNG_VER_MINOR   6
    #define PNG_LIBPNG_VER_RELEASE 7

    /* This should match the numeric part of the final component of
     * PNG_LIBPNG_VER_STRING, omitting any leading zero:
     */

    #define PNG_LIBPNG_VER_BUILD  0

    /* Release Status */
    #define PNG_LIBPNG_BUILD_ALPHA    1
    #define PNG_LIBPNG_BUILD_BETA     2
    #define PNG_LIBPNG_BUILD_RC       3
    #define PNG_LIBPNG_BUILD_STABLE   4
    #define PNG_LIBPNG_BUILD_RELEASE_STATUS_MASK 7

    /* Release-Specific Flags */
    #define PNG_LIBPNG_BUILD_PATCH    8 /* Can be OR'ed with
                                           PNG_LIBPNG_BUILD_STABLE only */
    #define PNG_LIBPNG_BUILD_PRIVATE 16 /* Cannot be OR'ed with
                                           PNG_LIBPNG_BUILD_SPECIAL */
    #define PNG_LIBPNG_BUILD_SPECIAL 32 /* Cannot be OR'ed with
                                           PNG_LIBPNG_BUILD_PRIVATE */

    #define PNG_LIBPNG_BUILD_BASE_TYPE PNG_LIBPNG_BUILD_STABLE

    /* Careful here.  At one time, Guy wanted to use 082, but that would be octal.
     * We must not include leading zeros.
     * Versions 0.7 through 1.0.0 were in the range 0 to 100 here (only
     * version 1.0.0 was mis-numbered 100 instead of 10000).  From
     * version 1.0.1 it's    xxyyzz, where x=major, y=minor, z=release
     */
    #define PNG_LIBPNG_VER 10607 /* 1.6.7 */

    /* Library configuration: these options cannot be changed after
     * the library has been built.
     */
    #ifndef PNGLCONF_H
        /* If pnglibconf.h is missing, you can
         * copy scripts/pnglibconf.h.prebuilt to pnglibconf.h
         */
    #   include "pnglibconf.h"
    #endif

    #ifndef PNG_VERSION_INFO_ONLY
       /* Machine specific configuration. */
    #  include "pngconf.h"
    #endif

    /*
     * Added at libpng-1.2.8
     *
     * Ref MSDN: Private as priority over Special
     * VS_FF_PRIVATEBUILD File *was not* built using standard release
     * procedures. If this value is given, the StringFileInfo block must
     * contain a PrivateBuild string.
     *
     * VS_FF_SPECIALBUILD File *was* built by the original company using
     * standard release procedures but is a variation of the standard
     * file of the same version number. If this value is given, the
     * StringFileInfo block must contain a SpecialBuild string.
     */

    #ifdef PNG_USER_PRIVATEBUILD /* From pnglibconf.h */
    #  define PNG_LIBPNG_BUILD_TYPE \
           (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_PRIVATE)
    #else
    #  ifdef PNG_LIBPNG_SPECIALBUILD
    #    define PNG_LIBPNG_BUILD_TYPE \
             (PNG_LIBPNG_BUILD_BASE_TYPE | PNG_LIBPNG_BUILD_SPECIAL)
    #  else
    #    define PNG_LIBPNG_BUILD_TYPE (PNG_LIBPNG_BUILD_BASE_TYPE)
    #  endif
    #endif

    #ifndef PNG_VERSION_INFO_ONLY

    /* Inhibit C++ name-mangling for libpng functions but not for system calls. */
    #ifdef __cplusplus
    extern "C" {
    #endif /* __cplusplus */

    /* Version information for C files, stored in png.c.  This had better match
     * the version above.
     */
    #define png_libpng_ver png_get_header_ver(NULL)

    /* This file is arranged in several sections:
     *
     * 1. Any configuration options that can be specified by for the application
     *    code when it is built.  (Build time configuration is in pnglibconf.h)
     * 2. Type definitions (base types are defined in pngconf.h), structure
     *    definitions.
     * 3. Exported library functions.
     * 4. Simplified API.
     *
     * The library source code has additional files (principally pngpriv.h) that
     * allow configuration of the library.
     */
    /* Section 1: run time configuration
     * See pnglibconf.h for build time configuration
     *
     * Run time configuration allows the application to choose between
     * implementations of certain arithmetic APIs.  The default is set
     * at build time and recorded in pnglibconf.h, but it is safe to
     * override these (and only these) settings.  Note that this won't
     * change what the library does, only application code, and the
     * settings can (and probably should) be made on a per-file basis
     * by setting the #defines before including png.h
     *
     * Use macros to read integers from PNG data or use the exported
     * functions?
     *   PNG_USE_READ_MACROS: use the macros (see below)  Note that
     *     the macros evaluate their argument multiple times.
     *   PNG_NO_USE_READ_MACROS: call the relevant library function.
     *
     * Use the alternative algorithm for compositing alpha samples that
     * does not use division?
     *   PNG_READ_COMPOSITE_NODIV_SUPPORTED: use the 'no division'
     *      algorithm.
     *   PNG_NO_READ_COMPOSITE_NODIV: use the 'division' algorithm.
     *
     * How to handle benign errors if PNG_ALLOW_BENIGN_ERRORS is
     * false?
     *   PNG_ALLOW_BENIGN_ERRORS: map calls to the benign error
     *      APIs to png_warning.
     * Otherwise the calls are mapped to png_error.
     */

    /* Section 2: type definitions, including structures and compile time
     * constants.
     * See pngconf.h for base types that vary by machine/system
     */

    /* This triggers a compiler error in png.c, if png.c and png.h
     * do not agree upon the version number.
     */
    typedef char* png_libpng_version_1_6_7;

    /* Basic control structions.  Read libpng-manual.txt or libpng.3 for more info.
     *
     * png_struct is the cache of information used while reading or writing a single
     * PNG file.  One of these is always required, although the simplified API
     * (below) hides the creation and destruction of it.
     */
    typedef struct png_struct_def png_struct;
    typedef const png_struct * png_const_structp;
    typedef png_struct * png_structp;
    typedef png_struct * * png_structpp;

    /* png_info contains information read from or to be written to a PNG file.  One
     * or more of these must exist while reading or creating a PNG file.  The
     * information is not used by libpng during read but is used to control what
     * gets written when a PNG file is created.  "png_get_" function calls read
     * information during read and "png_set_" functions calls write information
     * when creating a PNG.
     * been moved into a separate header file that is not accessible to
     * applications.  Read libpng-manual.txt or libpng.3 for more info.
     */
    typedef struct png_info_def png_info;
    typedef png_info * png_infop;
    typedef const png_info * png_const_infop;
    typedef png_info * * png_infopp;

    /* Types with names ending 'p' are pointer types.  The corresponding types with
     * names ending 'rp' are identical pointer types except that the pointer is
     * marked 'restrict', which means that it is the only pointer to the object
     * passed to the function.  Applications should not use the 'restrict' types;
     * it is always valid to pass 'p' to a pointer with a function argument of the
     * corresponding 'rp' type.  Different compilers have different rules with
     * regard to type matching in the presence of 'restrict'.  For backward
     * compatibility libpng callbacks never have 'restrict' in their parameters and,
     * consequentially, writing portable application code is extremely difficult if
     * an attempt is made to use 'restrict'.
     */
    typedef png_struct * PNG_RESTRICT png_structrp;
    typedef const png_struct * PNG_RESTRICT png_const_structrp;
    typedef png_info * PNG_RESTRICT png_inforp;
    typedef const png_info * PNG_RESTRICT png_const_inforp;

    /* Three color definitions.  The order of the red, green, and blue, (and the
     * exact size) is not important, although the size of the fields need to
     * be png_byte or png_uint_16 (as defined below).
     */
    typedef struct png_color_struct
    {
       png_byte red;
       png_byte green;
       png_byte blue;
    } png_color;
    typedef png_color * png_colorp;
    typedef const png_color * png_const_colorp;
    typedef png_color * * png_colorpp;

    typedef struct png_color_16_struct
    {
       png_byte index;    /* used for palette files */
       png_uint_16 red;   /* for use in red green blue files */
       png_uint_16 green;
       png_uint_16 blue;
       png_uint_16 gray;  /* for use in grayscale files */
    } png_color_16;
    typedef png_color_16 * png_color_16p;
    typedef const png_color_16 * png_const_color_16p;
    typedef png_color_16 * * png_color_16pp;

    typedef struct png_color_8_struct
    {
       png_byte red;   /* for use in red green blue files */
       png_byte green;
       png_byte blue;
       png_byte gray;  /* for use in grayscale files */
       png_byte alpha; /* for alpha channel files */
    } png_color_8;
    typedef png_color_8 * png_color_8p;
    typedef const png_color_8 * png_const_color_8p;
    typedef png_color_8 * * png_color_8pp;

    /*
     * The following two structures are used for the in-core representation
     * of sPLT chunks.
     */
    typedef struct png_sPLT_entry_struct
    {
       png_uint_16 red;
       png_uint_16 green;
       png_uint_16 blue;
       png_uint_16 alpha;
       png_uint_16 frequency;
    } png_sPLT_entry;
    typedef png_sPLT_entry * png_sPLT_entryp;
    typedef const png_sPLT_entry * png_const_sPLT_entryp;
    typedef png_sPLT_entry * * png_sPLT_entrypp;

    /*  When the depth of the sPLT palette is 8 bits, the color and alpha samples
     *  occupy the LSB of their respective members, and the MSB of each member
     *  is zero-filled.  The frequency member always occupies the full 16 bits.
     */

    typedef struct png_sPLT_struct
    {
       png_charp name;           /* palette name */
       png_byte depth;           /* depth of palette samples */
       png_sPLT_entryp entries;  /* palette entries */
       png_int_32 nentries;      /* number of palette entries */
    } png_sPLT_t;
    typedef png_sPLT_t * png_sPLT_tp;
    typedef const png_sPLT_t * png_const_sPLT_tp;
    typedef png_sPLT_t * * png_sPLT_tpp;

    #ifdef PNG_TEXT_SUPPORTED
    /* png_text holds the contents of a text/ztxt/itxt chunk in a PNG file,
     * and whether that contents is compressed or not.  The "key" field
     * points to a regular zero-terminated C string.  The "text" fields can be a
     * regular C string, an empty string, or a NULL pointer.
     * However, the structure returned by png_get_text() will always contain
     * the "text" field as a regular zero-terminated C string (possibly
     * empty), never a NULL pointer, so it can be safely used in printf() and
     * other string-handling functions.  Note that the "itxt_length", "lang", and
     * "lang_key" members of the structure only exist when the library is built
     * with iTXt chunk support.  Prior to libpng-1.4.0 the library was built by
     * default without iTXt support. Also note that when iTXt *is* supported,
     * the "lang" and "lang_key" fields contain NULL pointers when the
     * "compression" field contains * PNG_TEXT_COMPRESSION_NONE or
     * PNG_TEXT_COMPRESSION_zTXt. Note that the "compression value" is not the
     * same as what appears in the PNG tEXt/zTXt/iTXt chunk's "compression flag"
     * which is always 0 or 1, or its "compression method" which is always 0.
     */
    typedef struct png_text_struct
    {
       int  compression;       /* compression value:
                                 -1: tEXt, none
                                  0: zTXt, deflate
                                  1: iTXt, none
                                  2: iTXt, deflate  */
       png_charp key;          /* keyword, 1-79 character description of "text" */
       png_charp text;         /* comment, may be an empty string (ie "")
                                  or a NULL pointer */
       png_size_t text_length; /* length of the text string */
       png_size_t itxt_length; /* length of the itxt string */
       png_charp lang;         /* language code, 0-79 characters
                                  or a NULL pointer */
       png_charp lang_key;     /* keyword translated UTF-8 string, 0 or more
                                  chars or a NULL pointer */
    } png_text;
    typedef png_text * png_textp;
    typedef const png_text * png_const_textp;
    typedef png_text * * png_textpp;
    #endif

    /* Supported compression types for text in PNG files (tEXt, and zTXt).
     * The values of the PNG_TEXT_COMPRESSION_ defines should NOT be changed. */
    #define PNG_TEXT_COMPRESSION_NONE_WR -3
    #define PNG_TEXT_COMPRESSION_zTXt_WR -2
    #define PNG_TEXT_COMPRESSION_NONE    -1
    #define PNG_TEXT_COMPRESSION_zTXt     0
    #define PNG_ITXT_COMPRESSION_NONE     1
    #define PNG_ITXT_COMPRESSION_zTXt     2
    #define PNG_TEXT_COMPRESSION_LAST     3  /* Not a valid value */

    /* png_time is a way to hold the time in an machine independent way.
     * Two conversions are provided, both from time_t and struct tm.  There
     * is no portable way to convert to either of these structures, as far
     * as I know.  If you know of a portable way, send it to me.  As a side
     * note - PNG has always been Year 2000 compliant!
     */
    typedef struct png_time_struct
    {
       png_uint_16 year; /* full year, as in, 1995 */
       png_byte month;   /* month of year, 1 - 12 */
       png_byte day;     /* day of month, 1 - 31 */
       png_byte hour;    /* hour of day, 0 - 23 */
       png_byte minute;  /* minute of hour, 0 - 59 */
       png_byte second;  /* second of minute, 0 - 60 (for leap seconds) */
    } png_time;
    typedef png_time * png_timep;
    typedef const png_time * png_const_timep;
    typedef png_time * * png_timepp;

    #if defined(PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED) ||\
       defined(PNG_USER_CHUNKS_SUPPORTED)
    /* png_unknown_chunk is a structure to hold queued chunks for which there is
     * no specific support.  The idea is that we can use this to queue
     * up private chunks for output even though the library doesn't actually
     * know about their semantics.
     *
     * The data in the structure is set by libpng on read and used on write.
     */
    typedef struct png_unknown_chunk_t
    {
        png_byte name[5]; /* Textual chunk name with '\0' terminator */
        png_byte *data;   /* Data, should not be modified on read! */
        png_size_t size;

        /* On write 'location' must be set using the flag values listed below.
         * Notice that on read it is set by libpng however the values stored have
         * more bits set than are listed below.  Always treat the value as a
         * bitmask.  On write set only one bit - setting multiple bits may cause the
         * chunk to be written in multiple places.
         */
        png_byte location; /* mode of operation at read time */
    }
    png_unknown_chunk;

    typedef png_unknown_chunk * png_unknown_chunkp;
    typedef const png_unknown_chunk * png_const_unknown_chunkp;
    typedef png_unknown_chunk * * png_unknown_chunkpp;
    #endif

    /* Flag values for the unknown chunk location byte. */
    #define PNG_HAVE_IHDR  0x01
    #define PNG_HAVE_PLTE  0x02
    #define PNG_AFTER_IDAT 0x08

    /* Maximum positive integer used in PNG is (2^31)-1 */
    #define PNG_UINT_31_MAX ((png_uint_32)0x7fffffffL)
    #define PNG_UINT_32_MAX ((png_uint_32)(-1))
    #define PNG_SIZE_MAX ((png_size_t)(-1))

    /* These are constants for fixed point values encoded in the
     * PNG specification manner (x100000)
     */
    #define PNG_FP_1    100000
    #define PNG_FP_HALF  50000
    #define PNG_FP_MAX  ((png_fixed_point)0x7fffffffL)
    #define PNG_FP_MIN  (-PNG_FP_MAX)

    /* These describe the color_type field in png_info. */
    /* color type masks */
    #define PNG_COLOR_MASK_PALETTE    1
    #define PNG_COLOR_MASK_COLOR      2
    #define PNG_COLOR_MASK_ALPHA      4

    /* color types.  Note that not all combinations are legal */
    #define PNG_COLOR_TYPE_GRAY 0
    #define PNG_COLOR_TYPE_PALETTE  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)
    #define PNG_COLOR_TYPE_RGB        (PNG_COLOR_MASK_COLOR)
    #define PNG_COLOR_TYPE_RGB_ALPHA  (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_ALPHA)
    #define PNG_COLOR_TYPE_GRAY_ALPHA (PNG_COLOR_MASK_ALPHA)
    /* aliases */
    #define PNG_COLOR_TYPE_RGBA  PNG_COLOR_TYPE_RGB_ALPHA
    #define PNG_COLOR_TYPE_GA  PNG_COLOR_TYPE_GRAY_ALPHA

    /* This is for compression type. PNG 1.0-1.2 only define the single type. */
    #define PNG_COMPRESSION_TYPE_BASE 0 /* Deflate method 8, 32K window */
    #define PNG_COMPRESSION_TYPE_DEFAULT PNG_COMPRESSION_TYPE_BASE

    /* This is for filter type. PNG 1.0-1.2 only define the single type. */
    #define PNG_FILTER_TYPE_BASE      0 /* Single row per-byte filtering */
    #define PNG_INTRAPIXEL_DIFFERENCING 64 /* Used only in MNG datastreams */
    #define PNG_FILTER_TYPE_DEFAULT   PNG_FILTER_TYPE_BASE

    /* These are for the interlacing type.  These values should NOT be changed. */
    #define PNG_INTERLACE_NONE        0 /* Non-interlaced image */
    #define PNG_INTERLACE_ADAM7       1 /* Adam7 interlacing */
    #define PNG_INTERLACE_LAST        2 /* Not a valid value */

    /* These are for the oFFs chunk.  These values should NOT be changed. */
    #define PNG_OFFSET_PIXEL          0 /* Offset in pixels */
    #define PNG_OFFSET_MICROMETER     1 /* Offset in micrometers (1/10^6 meter) */
    #define PNG_OFFSET_LAST           2 /* Not a valid value */

    /* These are for the pCAL chunk.  These values should NOT be changed. */
    #define PNG_EQUATION_LINEAR       0 /* Linear transformation */
    #define PNG_EQUATION_BASE_E       1 /* Exponential base e transform */
    #define PNG_EQUATION_ARBITRARY    2 /* Arbitrary base exponential transform */
    #define PNG_EQUATION_HYPERBOLIC   3 /* Hyperbolic sine transformation */
    #define PNG_EQUATION_LAST         4 /* Not a valid value */

    /* These are for the sCAL chunk.  These values should NOT be changed. */
    #define PNG_SCALE_UNKNOWN         0 /* unknown unit (image scale) */
    #define PNG_SCALE_METER           1 /* meters per pixel */
    #define PNG_SCALE_RADIAN          2 /* radians per pixel */
    #define PNG_SCALE_LAST            3 /* Not a valid value */

    /* These are for the pHYs chunk.  These values should NOT be changed. */
    #define PNG_RESOLUTION_UNKNOWN    0 /* pixels/unknown unit (aspect ratio) */
    #define PNG_RESOLUTION_METER      1 /* pixels/meter */
    #define PNG_RESOLUTION_LAST       2 /* Not a valid value */

    /* These are for the sRGB chunk.  These values should NOT be changed. */
    #define PNG_sRGB_INTENT_PERCEPTUAL 0
    #define PNG_sRGB_INTENT_RELATIVE   1
    #define PNG_sRGB_INTENT_SATURATION 2
    #define PNG_sRGB_INTENT_ABSOLUTE   3
    #define PNG_sRGB_INTENT_LAST       4 /* Not a valid value */

    /* This is for text chunks */
    #define PNG_KEYWORD_MAX_LENGTH     79

    /* Maximum number of entries in PLTE/sPLT/tRNS arrays */
    #define PNG_MAX_PALETTE_LENGTH    256

    /* These determine if an ancillary chunk's data has been successfully read
     * from the PNG header, or if the application has filled in the corresponding
     * data in the info_struct to be written into the output file.  The values
     * of the PNG_INFO_<chunk> defines should NOT be changed.
     */
    #define PNG_INFO_gAMA 0x0001
    #define PNG_INFO_sBIT 0x0002
    #define PNG_INFO_cHRM 0x0004
    #define PNG_INFO_PLTE 0x0008
    #define PNG_INFO_tRNS 0x0010
    #define PNG_INFO_bKGD 0x0020
    #define PNG_INFO_hIST 0x0040
    #define PNG_INFO_pHYs 0x0080
    #define PNG_INFO_oFFs 0x0100
    #define PNG_INFO_tIME 0x0200
    #define PNG_INFO_pCAL 0x0400
    #define PNG_INFO_sRGB 0x0800   /* GR-P, 0.96a */
    #define PNG_INFO_iCCP 0x1000   /* ESR, 1.0.6 */
    #define PNG_INFO_sPLT 0x2000   /* ESR, 1.0.6 */
    #define PNG_INFO_sCAL 0x4000   /* ESR, 1.0.6 */
    #define PNG_INFO_IDAT 0x8000   /* ESR, 1.0.6 */

    /* This is used for the transformation routines, as some of them
     * change these values for the row.  It also should enable using
     * the routines for other purposes.
     */
    typedef struct png_row_info_struct
    {
       png_uint_32 width;    /* width of row */
       png_size_t rowbytes;  /* number of bytes in row */
       png_byte color_type;  /* color type of row */
       png_byte bit_depth;   /* bit depth of row */
       png_byte channels;    /* number of channels (1, 2, 3, or 4) */
       png_byte pixel_depth; /* bits per pixel (depth * channels) */
    } png_row_info;

    typedef png_row_info * png_row_infop;
    typedef png_row_info * * png_row_infopp;

    /* These are the function types for the I/O functions and for the functions
     * that allow the user to override the default I/O functions with his or her
     * own.  The png_error_ptr type should match that of user-supplied warning
     * and error functions, while the png_rw_ptr type should match that of the
     * user read/write data functions.  Note that the 'write' function must not
     * modify the buffer it is passed. The 'read' function, on the other hand, is
     * expected to return the read data in the buffer.
     */
    typedef PNG_CALLBACK(void, *png_error_ptr, (png_structp, png_const_charp));
    typedef PNG_CALLBACK(void, *png_rw_ptr, (png_structp, png_bytep, png_size_t));
    typedef PNG_CALLBACK(void, *png_flush_ptr, (png_structp));
    typedef PNG_CALLBACK(void, *png_read_status_ptr, (png_structp, png_uint_32,
        int));
    typedef PNG_CALLBACK(void, *png_write_status_ptr, (png_structp, png_uint_32,
        int));

    #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
    typedef PNG_CALLBACK(void, *png_progressive_info_ptr, (png_structp, png_infop));
    typedef PNG_CALLBACK(void, *png_progressive_end_ptr, (png_structp, png_infop));

    /* The following callback receives png_uint_32 row_number, int pass for the
     * png_bytep data of the row.  When transforming an interlaced image the
     * row number is the row number within the sub-image of the interlace pass, so
     * the value will increase to the height of the sub-image (not the full image)
     * then reset to 0 for the next pass.
     *
     * Use PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
     * find the output pixel (x,y) given an interlaced sub-image pixel
     * (row,col,pass).  (See below for these macros.)
     */
    typedef PNG_CALLBACK(void, *png_progressive_row_ptr, (png_structp, png_bytep,
        png_uint_32, int));
    #endif

    #if defined(PNG_READ_USER_TRANSFORM_SUPPORTED) || \
        defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
    typedef PNG_CALLBACK(void, *png_user_transform_ptr, (png_structp, png_row_infop,
        png_bytep));
    #endif

    #ifdef PNG_USER_CHUNKS_SUPPORTED
    typedef PNG_CALLBACK(int, *png_user_chunk_ptr, (png_structp,
        png_unknown_chunkp));
    #endif
    #ifdef PNG_UNKNOWN_CHUNKS_SUPPORTED
    /* not used anywhere */
    /* typedef PNG_CALLBACK(void, *png_unknown_chunk_ptr, (png_structp)); */
    #endif

    #ifdef PNG_SETJMP_SUPPORTED
    /* This must match the function definition in <setjmp.h>, and the application
     * must include this before png.h to obtain the definition of jmp_buf.  The
     * function is required to be PNG_NORETURN, but this is not checked.  If the
     * function does return the application will crash via an abort() or similar
     * system level call.
     *
     * If you get a warning here while building the library you may need to make
     * changes to ensure that pnglibconf.h records the calling convention used by
     * your compiler.  This may be very difficult - try using a different compiler
     * to build the library!
     */
    PNG_FUNCTION(void, (PNGCAPI *png_longjmp_ptr), PNGARG((jmp_buf, int)), typedef);
    #endif

    /* Transform masks for the high-level interface */
    #define PNG_TRANSFORM_IDENTITY       0x0000    /* read and write */
    #define PNG_TRANSFORM_STRIP_16       0x0001    /* read only */
    #define PNG_TRANSFORM_STRIP_ALPHA    0x0002    /* read only */
    #define PNG_TRANSFORM_PACKING        0x0004    /* read and write */
    #define PNG_TRANSFORM_PACKSWAP       0x0008    /* read and write */
    #define PNG_TRANSFORM_EXPAND         0x0010    /* read only */
    #define PNG_TRANSFORM_INVERT_MONO    0x0020    /* read and write */
    #define PNG_TRANSFORM_SHIFT          0x0040    /* read and write */
    #define PNG_TRANSFORM_BGR            0x0080    /* read and write */
    #define PNG_TRANSFORM_SWAP_ALPHA     0x0100    /* read and write */
    #define PNG_TRANSFORM_SWAP_ENDIAN    0x0200    /* read and write */
    #define PNG_TRANSFORM_INVERT_ALPHA   0x0400    /* read and write */
    #define PNG_TRANSFORM_STRIP_FILLER   0x0800    /* write only */
    /* Added to libpng-1.2.34 */
    #define PNG_TRANSFORM_STRIP_FILLER_BEFORE PNG_TRANSFORM_STRIP_FILLER
    #define PNG_TRANSFORM_STRIP_FILLER_AFTER 0x1000 /* write only */
    /* Added to libpng-1.4.0 */
    #define PNG_TRANSFORM_GRAY_TO_RGB   0x2000      /* read only */
    /* Added to libpng-1.5.4 */
    #define PNG_TRANSFORM_EXPAND_16     0x4000      /* read only */
    #define PNG_TRANSFORM_SCALE_16      0x8000      /* read only */

    /* Flags for MNG supported features */
    #define PNG_FLAG_MNG_EMPTY_PLTE     0x01
    #define PNG_FLAG_MNG_FILTER_64      0x04
    #define PNG_ALL_MNG_FEATURES        0x05

    /* NOTE: prior to 1.5 these functions had no 'API' style declaration,
     * this allowed the zlib default functions to be used on Windows
     * platforms.  In 1.5 the zlib default malloc (which just calls malloc and
     * ignores the first argument) should be completely compatible with the
     * following.
     */
    typedef PNG_CALLBACK(png_voidp, *png_malloc_ptr, (png_structp,
        png_alloc_size_t));
    typedef PNG_CALLBACK(void, *png_free_ptr, (png_structp, png_voidp));

    /* Section 3: exported functions
     * Here are the function definitions most commonly used.  This is not
     * the place to find out how to use libpng.  See libpng-manual.txt for the
     * full explanation, see example.c for the summary.  This just provides
     * a simple one line description of the use of each function.
     *
     * The PNG_EXPORT() and PNG_EXPORTA() macros used below are defined in
     * pngconf.h and in the *.dfn files in the scripts directory.
     *
     *   PNG_EXPORT(ordinal, type, name, (args));
     *
     *       ordinal:    ordinal that is used while building
     *                   *.def files. The ordinal value is only
     *                   relevant when preprocessing png.h with
     *                   the *.dfn files for building symbol table
     *                   entries, and are removed by pngconf.h.
     *       type:       return type of the function
     *       name:       function name
     *       args:       function arguments, with types
     *
     * When we wish to append attributes to a function prototype we use
     * the PNG_EXPORTA() macro instead.
     *
     *   PNG_EXPORTA(ordinal, type, name, (args), attributes);
     *
     *       ordinal, type, name, and args: same as in PNG_EXPORT().
     *       attributes: function attributes
     */

    /* Returns the version number of the library */
    PNG_EXPORT(1, png_uint_32, png_access_version_number, (void));

    /* Tell lib we have already handled the first <num_bytes> magic bytes.
     * Handling more than 8 bytes from the beginning of the file is an error.
     */
    PNG_EXPORT(2, void, png_set_sig_bytes, (png_structrp png_ptr, int num_bytes));

    /* Check sig[start] through sig[start + num_to_check - 1] to see if it's a
     * PNG file.  Returns zero if the supplied bytes match the 8-byte PNG
     * signature, and non-zero otherwise.  Having num_to_check == 0 or
     * start > 7 will always fail (ie return non-zero).
     */
    PNG_EXPORT(3, int, png_sig_cmp, (png_const_bytep sig, png_size_t start,
        png_size_t num_to_check));

    /* Simple signature checking function.  This is the same as calling
     * png_check_sig(sig, n) := !png_sig_cmp(sig, 0, n).
     */
    #define png_check_sig(sig, n) !png_sig_cmp((sig), 0, (n))

    /* Allocate and initialize png_ptr struct for reading, and any other memory. */
    PNG_EXPORTA(4, png_structp, png_create_read_struct,
        (png_const_charp user_png_ver, png_voidp error_ptr,
        png_error_ptr error_fn, png_error_ptr warn_fn),
        PNG_ALLOCATED);

    /* Allocate and initialize png_ptr struct for writing, and any other memory */
    PNG_EXPORTA(5, png_structp, png_create_write_struct,
        (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
        png_error_ptr warn_fn),
        PNG_ALLOCATED);

    PNG_EXPORT(6, png_size_t, png_get_compression_buffer_size,
        (png_const_structrp png_ptr));

    PNG_EXPORT(7, void, png_set_compression_buffer_size, (png_structrp png_ptr,
        png_size_t size));

    /* Moved from pngconf.h in 1.4.0 and modified to ensure setjmp/longjmp
     * match up.
     */
    #ifdef PNG_SETJMP_SUPPORTED
    /* This function returns the jmp_buf built in to *png_ptr.  It must be
     * supplied with an appropriate 'longjmp' function to use on that jmp_buf
     * unless the default error function is overridden in which case NULL is
     * acceptable.  The size of the jmp_buf is checked against the actual size
     * allocated by the library - the call will return NULL on a mismatch
     * indicating an ABI mismatch.
     */
    PNG_EXPORT(8, jmp_buf*, png_set_longjmp_fn, (png_structrp png_ptr,
        png_longjmp_ptr longjmp_fn, size_t jmp_buf_size));
    #  define png_jmpbuf(png_ptr) \
          (*png_set_longjmp_fn((png_ptr), longjmp, (sizeof (jmp_buf))))
    #else
    #  define png_jmpbuf(png_ptr) \
          (LIBPNG_WAS_COMPILED_WITH__PNG_NO_SETJMP)
    #endif
    /* This function should be used by libpng applications in place of
     * longjmp(png_ptr->jmpbuf, val).  If longjmp_fn() has been set, it
     * will use it; otherwise it will call PNG_ABORT().  This function was
     * added in libpng-1.5.0.
     */
    PNG_EXPORTA(9, void, png_longjmp, (png_const_structrp png_ptr, int val),
        PNG_NORETURN);

    #ifdef PNG_READ_SUPPORTED
    /* Reset the compression stream */
    PNG_EXPORTA(10, int, png_reset_zstream, (png_structrp png_ptr), PNG_DEPRECATED);
    #endif

    /* New functions added in libpng-1.0.2 (not enabled by default until 1.2.0) */
    #ifdef PNG_USER_MEM_SUPPORTED
    PNG_EXPORTA(11, png_structp, png_create_read_struct_2,
        (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
        png_error_ptr warn_fn,
        png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn),
        PNG_ALLOCATED);
    PNG_EXPORTA(12, png_structp, png_create_write_struct_2,
        (png_const_charp user_png_ver, png_voidp error_ptr, png_error_ptr error_fn,
        png_error_ptr warn_fn,
        png_voidp mem_ptr, png_malloc_ptr malloc_fn, png_free_ptr free_fn),
        PNG_ALLOCATED);
    #endif

    /* Write the PNG file signature. */
    PNG_EXPORT(13, void, png_write_sig, (png_structrp png_ptr));

    /* Write a PNG chunk - size, type, (optional) data, CRC. */
    PNG_EXPORT(14, void, png_write_chunk, (png_structrp png_ptr, png_const_bytep
        chunk_name, png_const_bytep data, png_size_t length));

    /* Write the start of a PNG chunk - length and chunk name. */
    PNG_EXPORT(15, void, png_write_chunk_start, (png_structrp png_ptr,
        png_const_bytep chunk_name, png_uint_32 length));

    /* Write the data of a PNG chunk started with png_write_chunk_start(). */
    PNG_EXPORT(16, void, png_write_chunk_data, (png_structrp png_ptr,
        png_const_bytep data, png_size_t length));

    /* Finish a chunk started with png_write_chunk_start() (includes CRC). */
    PNG_EXPORT(17, void, png_write_chunk_end, (png_structrp png_ptr));

    /* Allocate and initialize the info structure */
    PNG_EXPORTA(18, png_infop, png_create_info_struct, (png_const_structrp png_ptr),
        PNG_ALLOCATED);

    /* DEPRECATED: this function allowed init structures to be created using the
     * default allocation method (typically malloc).  Use is deprecated in 1.6.0 and
     * the API will be removed in the future.
     */
    PNG_EXPORTA(19, void, png_info_init_3, (png_infopp info_ptr,
        png_size_t png_info_struct_size), PNG_DEPRECATED);

    /* Writes all the PNG information before the image. */
    PNG_EXPORT(20, void, png_write_info_before_PLTE,
        (png_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(21, void, png_write_info,
        (png_structrp png_ptr, png_const_inforp info_ptr));

    #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
    /* Read the information before the actual image data. */
    PNG_EXPORT(22, void, png_read_info,
        (png_structrp png_ptr, png_inforp info_ptr));
    #endif

    #ifdef PNG_TIME_RFC1123_SUPPORTED
       /* Convert to a US string format: there is no localization support in this
        * routine.  The original implementation used a 29 character buffer in
        * png_struct, this will be removed in future versions.
        */
    #if PNG_LIBPNG_VER < 10700
    /* To do: remove this from libpng17 (and from libpng17/png.c and pngstruct.h) */
    PNG_EXPORTA(23, png_const_charp, png_convert_to_rfc1123, (png_structrp png_ptr,
        png_const_timep ptime),PNG_DEPRECATED);
    #endif
    PNG_EXPORT(241, int, png_convert_to_rfc1123_buffer, (char out[29],
        png_const_timep ptime));
    #endif

    #ifdef PNG_CONVERT_tIME_SUPPORTED
    /* Convert from a struct tm to png_time */
    PNG_EXPORT(24, void, png_convert_from_struct_tm, (png_timep ptime,
        const struct tm * ttime));

    /* Convert from time_t to png_time.  Uses gmtime() */
    PNG_EXPORT(25, void, png_convert_from_time_t, (png_timep ptime, time_t ttime));
    #endif /* PNG_CONVERT_tIME_SUPPORTED */

    #ifdef PNG_READ_EXPAND_SUPPORTED
    /* Expand data to 24-bit RGB, or 8-bit grayscale, with alpha if available. */
    PNG_EXPORT(26, void, png_set_expand, (png_structrp png_ptr));
    PNG_EXPORT(27, void, png_set_expand_gray_1_2_4_to_8, (png_structrp png_ptr));
    PNG_EXPORT(28, void, png_set_palette_to_rgb, (png_structrp png_ptr));
    PNG_EXPORT(29, void, png_set_tRNS_to_alpha, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_EXPAND_16_SUPPORTED
    /* Expand to 16-bit channels, forces conversion of palette to RGB and expansion
     * of a tRNS chunk if present.
     */
    PNG_EXPORT(221, void, png_set_expand_16, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
    /* Use blue, green, red order for pixels. */
    PNG_EXPORT(30, void, png_set_bgr, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
    /* Expand the grayscale to 24-bit RGB if necessary. */
    PNG_EXPORT(31, void, png_set_gray_to_rgb, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
    /* Reduce RGB to grayscale. */
    #define PNG_ERROR_ACTION_NONE  1
    #define PNG_ERROR_ACTION_WARN  2
    #define PNG_ERROR_ACTION_ERROR 3
    #define PNG_RGB_TO_GRAY_DEFAULT (-1)/*for red/green coefficients*/

    PNG_FP_EXPORT(32, void, png_set_rgb_to_gray, (png_structrp png_ptr,
        int error_action, double red, double green))
    PNG_FIXED_EXPORT(33, void, png_set_rgb_to_gray_fixed, (png_structrp png_ptr,
        int error_action, png_fixed_point red, png_fixed_point green))

    PNG_EXPORT(34, png_byte, png_get_rgb_to_gray_status, (png_const_structrp
        png_ptr));
    #endif

    #ifdef PNG_BUILD_GRAYSCALE_PALETTE_SUPPORTED
    PNG_EXPORT(35, void, png_build_grayscale_palette, (int bit_depth,
        png_colorp palette));
    #endif

    #ifdef PNG_READ_ALPHA_MODE_SUPPORTED
    /* How the alpha channel is interpreted - this affects how the color channels of
     * a PNG file are returned when an alpha channel, or tRNS chunk in a palette
     * file, is present.
     *
     * This has no effect on the way pixels are written into a PNG output
     * datastream. The color samples in a PNG datastream are never premultiplied
     * with the alpha samples.
     *
     * The default is to return data according to the PNG specification: the alpha
     * channel is a linear measure of the contribution of the pixel to the
     * corresponding composited pixel.  The gamma encoded color channels must be
     * scaled according to the contribution and to do this it is necessary to undo
     * the encoding, scale the color values, perform the composition and reencode
     * the values.  This is the 'PNG' mode.
     *
     * The alternative is to 'associate' the alpha with the color information by
     * storing color channel values that have been scaled by the alpha.  The
     * advantage is that the color channels can be resampled (the image can be
     * scaled) in this form.  The disadvantage is that normal practice is to store
     * linear, not (gamma) encoded, values and this requires 16-bit channels for
     * still images rather than the 8-bit channels that are just about sufficient if
     * gamma encoding is used.  In addition all non-transparent pixel values,
     * including completely opaque ones, must be gamma encoded to produce the final
     * image.  This is the 'STANDARD', 'ASSOCIATED' or 'PREMULTIPLIED' mode (the
     * latter being the two common names for associated alpha color channels.)
     *
     * Since it is not necessary to perform arithmetic on opaque color values so
     * long as they are not to be resampled and are in the final color space it is
     * possible to optimize the handling of alpha by storing the opaque pixels in
     * the PNG format (adjusted for the output color space) while storing partially
     * opaque pixels in the standard, linear, format.  The accuracy required for
     * standard alpha composition is relatively low, because the pixels are
     * isolated, therefore typically the accuracy loss in storing 8-bit linear
     * values is acceptable.  (This is not true if the alpha channel is used to
     * simulate transparency over large areas - use 16 bits or the PNG mode in
     * this case!)  This is the 'OPTIMIZED' mode.  For this mode a pixel is
     * treated as opaque only if the alpha value is equal to the maximum value.
     *
     * The final choice is to gamma encode the alpha channel as well.  This is
     * broken because, in practice, no implementation that uses this choice
     * correctly undoes the encoding before handling alpha composition.  Use this
     * choice only if other serious errors in the software or hardware you use
     * mandate it; the typical serious error is for dark halos to appear around
     * opaque areas of the composited PNG image because of arithmetic overflow.
     *
     * The API function png_set_alpha_mode specifies which of these choices to use
     * with an enumerated 'mode' value and the gamma of the required output:
     */
    #define PNG_ALPHA_PNG           0 /* according to the PNG standard */
    #define PNG_ALPHA_STANDARD      1 /* according to Porter/Duff */
    #define PNG_ALPHA_ASSOCIATED    1 /* as above; this is the normal practice */
    #define PNG_ALPHA_PREMULTIPLIED 1 /* as above */
    #define PNG_ALPHA_OPTIMIZED     2 /* 'PNG' for opaque pixels, else 'STANDARD' */
    #define PNG_ALPHA_BROKEN        3 /* the alpha channel is gamma encoded */

    PNG_FP_EXPORT(227, void, png_set_alpha_mode, (png_structrp png_ptr, int mode,
        double output_gamma))
    PNG_FIXED_EXPORT(228, void, png_set_alpha_mode_fixed, (png_structrp png_ptr,
        int mode, png_fixed_point output_gamma))
    #endif

    #if defined(PNG_GAMMA_SUPPORTED) || defined(PNG_READ_ALPHA_MODE_SUPPORTED)
    /* The output_gamma value is a screen gamma in libpng terminology: it expresses
     * how to decode the output values, not how they are encoded.  The values used
     * correspond to the normal numbers used to describe the overall gamma of a
     * computer display system; for example 2.2 for an sRGB conformant system.  The
     * values are scaled by 100000 in the _fixed version of the API (so 220000 for
     * sRGB.)
     *
     * The inverse of the value is always used to provide a default for the PNG file
     * encoding if it has no gAMA chunk and if png_set_gamma() has not been called
     * to override the PNG gamma information.
     *
     * When the ALPHA_OPTIMIZED mode is selected the output gamma is used to encode
     * opaque pixels however pixels with lower alpha values are not encoded,
     * regardless of the output gamma setting.
     *
     * When the standard Porter Duff handling is requested with mode 1 the output
     * encoding is set to be linear and the output_gamma value is only relevant
     * as a default for input data that has no gamma information.  The linear output
     * encoding will be overridden if png_set_gamma() is called - the results may be
     * highly unexpected!
     *
     * The following numbers are derived from the sRGB standard and the research
     * behind it.  sRGB is defined to be approximated by a PNG gAMA chunk value of
     * 0.45455 (1/2.2) for PNG.  The value implicitly includes any viewing
     * correction required to take account of any differences in the color
     * environment of the original scene and the intended display environment; the
     * value expresses how to *decode* the image for display, not how the original
     * data was *encoded*.
     *
     * sRGB provides a peg for the PNG standard by defining a viewing environment.
     * sRGB itself, and earlier TV standards, actually use a more complex transform
     * (a linear portion then a gamma 2.4 power law) than PNG can express.  (PNG is
     * limited to simple power laws.)  By saying that an image for direct display on
     * an sRGB conformant system should be stored with a gAMA chunk value of 45455
     * (11.3.3.2 and 11.3.3.5 of the ISO PNG specification) the PNG specification
     * makes it possible to derive values for other display systems and
     * environments.
     *
     * The Mac value is deduced from the sRGB based on an assumption that the actual
     * extra viewing correction used in early Mac display systems was implemented as
     * a power 1.45 lookup table.
     *
     * Any system where a programmable lookup table is used or where the behavior of
     * the final display device characteristics can be changed requires system
     * specific code to obtain the current characteristic.  However this can be
     * difficult and most PNG gamma correction only requires an approximate value.
     *
     * By default, if png_set_alpha_mode() is not called, libpng assumes that all
     * values are unencoded, linear, values and that the output device also has a
     * linear characteristic.  This is only very rarely correct - it is invariably
     * better to call png_set_alpha_mode() with PNG_DEFAULT_sRGB than rely on the
     * default if you don't know what the right answer is!
     *
     * The special value PNG_GAMMA_MAC_18 indicates an older Mac system (pre Mac OS
     * 10.6) which used a correction table to implement a somewhat lower gamma on an
     * otherwise sRGB system.
     *
     * Both these values are reserved (not simple gamma values) in order to allow
     * more precise correction internally in the future.
     *
     * NOTE: the following values can be passed to either the fixed or floating
     * point APIs, but the floating point API will also accept floating point
     * values.
     */
    #define PNG_DEFAULT_sRGB -1       /* sRGB gamma and color space */
    #define PNG_GAMMA_MAC_18 -2       /* Old Mac '1.8' gamma and color space */
    #define PNG_GAMMA_sRGB   220000   /* Television standards--matches sRGB gamma */
    #define PNG_GAMMA_LINEAR PNG_FP_1 /* Linear */
    #endif

    /* The following are examples of calls to png_set_alpha_mode to achieve the
     * required overall gamma correction and, where necessary, alpha
     * premultiplication.
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
     *    This is the default libpng handling of the alpha channel - it is not
     *    pre-multiplied into the color components.  In addition the call states
     *    that the output is for a sRGB system and causes all PNG files without gAMA
     *    chunks to be assumed to be encoded using sRGB.
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
     *    In this case the output is assumed to be something like an sRGB conformant
     *    display preceeded by a power-law lookup table of power 1.45.  This is how
     *    early Mac systems behaved.
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_GAMMA_LINEAR);
     *    This is the classic Jim Blinn approach and will work in academic
     *    environments where everything is done by the book.  It has the shortcoming
     *    of assuming that input PNG data with no gamma information is linear - this
     *    is unlikely to be correct unless the PNG files where generated locally.
     *    Most of the time the output precision will be so low as to show
     *    significant banding in dark areas of the image.
     *
     * png_set_expand_16(pp);
     * png_set_alpha_mode(pp, PNG_ALPHA_STANDARD, PNG_DEFAULT_sRGB);
     *    This is a somewhat more realistic Jim Blinn inspired approach.  PNG files
     *    are assumed to have the sRGB encoding if not marked with a gamma value and
     *    the output is always 16 bits per component.  This permits accurate scaling
     *    and processing of the data.  If you know that your input PNG files were
     *    generated locally you might need to replace PNG_DEFAULT_sRGB with the
     *    correct value for your system.
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_OPTIMIZED, PNG_DEFAULT_sRGB);
     *    If you just need to composite the PNG image onto an existing background
     *    and if you control the code that does this you can use the optimization
     *    setting.  In this case you just copy completely opaque pixels to the
     *    output.  For pixels that are not completely transparent (you just skip
     *    those) you do the composition math using png_composite or png_composite_16
     *    below then encode the resultant 8-bit or 16-bit values to match the output
     *    encoding.
     *
     * Other cases
     *    If neither the PNG nor the standard linear encoding work for you because
     *    of the software or hardware you use then you have a big problem.  The PNG
     *    case will probably result in halos around the image.  The linear encoding
     *    will probably result in a washed out, too bright, image (it's actually too
     *    contrasty.)  Try the ALPHA_OPTIMIZED mode above - this will probably
     *    substantially reduce the halos.  Alternatively try:
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_BROKEN, PNG_DEFAULT_sRGB);
     *    This option will also reduce the halos, but there will be slight dark
     *    halos round the opaque parts of the image where the background is light.
     *    In the OPTIMIZED mode the halos will be light halos where the background
     *    is dark.  Take your pick - the halos are unavoidable unless you can get
     *    your hardware/software fixed!  (The OPTIMIZED approach is slightly
     *    faster.)
     *
     * When the default gamma of PNG files doesn't match the output gamma.
     *    If you have PNG files with no gamma information png_set_alpha_mode allows
     *    you to provide a default gamma, but it also sets the ouput gamma to the
     *    matching value.  If you know your PNG files have a gamma that doesn't
     *    match the output you can take advantage of the fact that
     *    png_set_alpha_mode always sets the output gamma but only sets the PNG
     *    default if it is not already set:
     *
     * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_DEFAULT_sRGB);
     * png_set_alpha_mode(pp, PNG_ALPHA_PNG, PNG_GAMMA_MAC);
     *    The first call sets both the default and the output gamma values, the
     *    second call overrides the output gamma without changing the default.  This
     *    is easier than achieving the same effect with png_set_gamma.  You must use
     *    PNG_ALPHA_PNG for the first call - internal checking in png_set_alpha will
     *    fire if more than one call to png_set_alpha_mode and png_set_background is
     *    made in the same read operation, however multiple calls with PNG_ALPHA_PNG
     *    are ignored.
     */

    #ifdef PNG_READ_STRIP_ALPHA_SUPPORTED
    PNG_EXPORT(36, void, png_set_strip_alpha, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_SWAP_ALPHA_SUPPORTED) || \
        defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
    PNG_EXPORT(37, void, png_set_swap_alpha, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_INVERT_ALPHA_SUPPORTED) || \
        defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
    PNG_EXPORT(38, void, png_set_invert_alpha, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_FILLER_SUPPORTED) || defined(PNG_WRITE_FILLER_SUPPORTED)
    /* Add a filler byte to 8-bit Gray or 24-bit RGB images. */
    PNG_EXPORT(39, void, png_set_filler, (png_structrp png_ptr, png_uint_32 filler,
        int flags));
    /* The values of the PNG_FILLER_ defines should NOT be changed */
    #  define PNG_FILLER_BEFORE 0
    #  define PNG_FILLER_AFTER 1
    /* Add an alpha byte to 8-bit Gray or 24-bit RGB images. */
    PNG_EXPORT(40, void, png_set_add_alpha, (png_structrp png_ptr,
        png_uint_32 filler, int flags));
    #endif /* PNG_READ_FILLER_SUPPORTED || PNG_WRITE_FILLER_SUPPORTED */

    #if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
    /* Swap bytes in 16-bit depth files. */
    PNG_EXPORT(41, void, png_set_swap, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_PACK_SUPPORTED) || defined(PNG_WRITE_PACK_SUPPORTED)
    /* Use 1 byte per pixel in 1, 2, or 4-bit depth files. */
    PNG_EXPORT(42, void, png_set_packing, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_PACKSWAP_SUPPORTED) || \
        defined(PNG_WRITE_PACKSWAP_SUPPORTED)
    /* Swap packing order of pixels in bytes. */
    PNG_EXPORT(43, void, png_set_packswap, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_SHIFT_SUPPORTED) || defined(PNG_WRITE_SHIFT_SUPPORTED)
    /* Converts files to legal bit depths. */
    PNG_EXPORT(44, void, png_set_shift, (png_structrp png_ptr, png_const_color_8p
        true_bits));
    #endif

    #if defined(PNG_READ_INTERLACING_SUPPORTED) || \
        defined(PNG_WRITE_INTERLACING_SUPPORTED)
    /* Have the code handle the interlacing.  Returns the number of passes.
     * MUST be called before png_read_update_info or png_start_read_image,
     * otherwise it will not have the desired effect.  Note that it is still
     * necessary to call png_read_row or png_read_rows png_get_image_height
     * times for each pass.
    */
    PNG_EXPORT(45, int, png_set_interlace_handling, (png_structrp png_ptr));
    #endif

    #if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
    /* Invert monochrome files */
    PNG_EXPORT(46, void, png_set_invert_mono, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_BACKGROUND_SUPPORTED
    /* Handle alpha and tRNS by replacing with a background color.  Prior to
     * libpng-1.5.4 this API must not be called before the PNG file header has been
     * read.  Doing so will result in unexpected behavior and possible warnings or
     * errors if the PNG file contains a bKGD chunk.
     */
    PNG_FP_EXPORT(47, void, png_set_background, (png_structrp png_ptr,
        png_const_color_16p background_color, int background_gamma_code,
        int need_expand, double background_gamma))
    PNG_FIXED_EXPORT(215, void, png_set_background_fixed, (png_structrp png_ptr,
        png_const_color_16p background_color, int background_gamma_code,
        int need_expand, png_fixed_point background_gamma))
    #endif
    #ifdef PNG_READ_BACKGROUND_SUPPORTED
    #  define PNG_BACKGROUND_GAMMA_UNKNOWN 0
    #  define PNG_BACKGROUND_GAMMA_SCREEN  1
    #  define PNG_BACKGROUND_GAMMA_FILE    2
    #  define PNG_BACKGROUND_GAMMA_UNIQUE  3
    #endif

    #ifdef PNG_READ_SCALE_16_TO_8_SUPPORTED
    /* Scale a 16-bit depth file down to 8-bit, accurately. */
    PNG_EXPORT(229, void, png_set_scale_16, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_STRIP_16_TO_8_SUPPORTED
    #define PNG_READ_16_TO_8 SUPPORTED /* Name prior to 1.5.4 */
    /* Strip the second byte of information from a 16-bit depth file. */
    PNG_EXPORT(48, void, png_set_strip_16, (png_structrp png_ptr));
    #endif

    #ifdef PNG_READ_QUANTIZE_SUPPORTED
    /* Turn on quantizing, and reduce the palette to the number of colors
     * available.
     */
    PNG_EXPORT(49, void, png_set_quantize, (png_structrp png_ptr,
        png_colorp palette, int num_palette, int maximum_colors,
        png_const_uint_16p histogram, int full_quantize));
    #endif

    #ifdef PNG_READ_GAMMA_SUPPORTED
    /* The threshold on gamma processing is configurable but hard-wired into the
     * library.  The following is the floating point variant.
     */
    #define PNG_GAMMA_THRESHOLD (PNG_GAMMA_THRESHOLD_FIXED*.00001)

    /* Handle gamma correction. Screen_gamma=(display_exponent).
     * NOTE: this API simply sets the screen and file gamma values. It will
     * therefore override the value for gamma in a PNG file if it is called after
     * the file header has been read - use with care  - call before reading the PNG
     * file for best results!
     *
     * These routines accept the same gamma values as png_set_alpha_mode (described
     * above).  The PNG_GAMMA_ defines and PNG_DEFAULT_sRGB can be passed to either
     * API (floating point or fixed.)  Notice, however, that the 'file_gamma' value
     * is the inverse of a 'screen gamma' value.
     */
    PNG_FP_EXPORT(50, void, png_set_gamma, (png_structrp png_ptr,
        double screen_gamma, double override_file_gamma))
    PNG_FIXED_EXPORT(208, void, png_set_gamma_fixed, (png_structrp png_ptr,
        png_fixed_point screen_gamma, png_fixed_point override_file_gamma))
    #endif

    #ifdef PNG_WRITE_FLUSH_SUPPORTED
    /* Set how many lines between output flushes - 0 for no flushing */
    PNG_EXPORT(51, void, png_set_flush, (png_structrp png_ptr, int nrows));
    /* Flush the current PNG output buffer */
    PNG_EXPORT(52, void, png_write_flush, (png_structrp png_ptr));
    #endif

    /* Optional update palette with requested transformations */
    PNG_EXPORT(53, void, png_start_read_image, (png_structrp png_ptr));

    /* Optional call to update the users info structure */
    PNG_EXPORT(54, void, png_read_update_info, (png_structrp png_ptr,
        png_inforp info_ptr));

    #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
    /* Read one or more rows of image data. */
    PNG_EXPORT(55, void, png_read_rows, (png_structrp png_ptr, png_bytepp row,
        png_bytepp display_row, png_uint_32 num_rows));
    #endif

    #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
    /* Read a row of data. */
    PNG_EXPORT(56, void, png_read_row, (png_structrp png_ptr, png_bytep row,
        png_bytep display_row));
    #endif

    #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
    /* Read the whole image into memory at once. */
    PNG_EXPORT(57, void, png_read_image, (png_structrp png_ptr, png_bytepp image));
    #endif

    /* Write a row of image data */
    PNG_EXPORT(58, void, png_write_row, (png_structrp png_ptr,
        png_const_bytep row));

    /* Write a few rows of image data: (*row) is not written; however, the type
     * is declared as writeable to maintain compatibility with previous versions
     * of libpng and to allow the 'display_row' array from read_rows to be passed
     * unchanged to write_rows.
     */
    PNG_EXPORT(59, void, png_write_rows, (png_structrp png_ptr, png_bytepp row,
        png_uint_32 num_rows));

    /* Write the image data */
    PNG_EXPORT(60, void, png_write_image, (png_structrp png_ptr, png_bytepp image));

    /* Write the end of the PNG file. */
    PNG_EXPORT(61, void, png_write_end, (png_structrp png_ptr,
        png_inforp info_ptr));

    #ifdef PNG_SEQUENTIAL_READ_SUPPORTED
    /* Read the end of the PNG file. */
    PNG_EXPORT(62, void, png_read_end, (png_structrp png_ptr, png_inforp info_ptr));
    #endif

    /* Free any memory associated with the png_info_struct */
    PNG_EXPORT(63, void, png_destroy_info_struct, (png_const_structrp png_ptr,
        png_infopp info_ptr_ptr));

    /* Free any memory associated with the png_struct and the png_info_structs */
    PNG_EXPORT(64, void, png_destroy_read_struct, (png_structpp png_ptr_ptr,
        png_infopp info_ptr_ptr, png_infopp end_info_ptr_ptr));

    /* Free any memory associated with the png_struct and the png_info_structs */
    PNG_EXPORT(65, void, png_destroy_write_struct, (png_structpp png_ptr_ptr,
        png_infopp info_ptr_ptr));

    /* Set the libpng method of handling chunk CRC errors */
    PNG_EXPORT(66, void, png_set_crc_action, (png_structrp png_ptr, int crit_action,
        int ancil_action));

    /* Values for png_set_crc_action() say how to handle CRC errors in
     * ancillary and critical chunks, and whether to use the data contained
     * therein.  Note that it is impossible to "discard" data in a critical
     * chunk.  For versions prior to 0.90, the action was always error/quit,
     * whereas in version 0.90 and later, the action for CRC errors in ancillary
     * chunks is warn/discard.  These values should NOT be changed.
     *
     *      value                       action:critical     action:ancillary
     */
    #define PNG_CRC_DEFAULT       0  /* error/quit          warn/discard data */
    #define PNG_CRC_ERROR_QUIT    1  /* error/quit          error/quit        */
    #define PNG_CRC_WARN_DISCARD  2  /* (INVALID)           warn/discard data */
    #define PNG_CRC_WARN_USE      3  /* warn/use data       warn/use data     */
    #define PNG_CRC_QUIET_USE     4  /* quiet/use data      quiet/use data    */
    #define PNG_CRC_NO_CHANGE     5  /* use current value   use current value */

    /* These functions give the user control over the scan-line filtering in
     * libpng and the compression methods used by zlib.  These functions are
     * mainly useful for testing, as the defaults should work with most users.
     * Those users who are tight on memory or want faster performance at the
     * expense of compression can modify them.  See the compression library
     * header file (zlib.h) for an explination of the compression functions.
     */

    /* Set the filtering method(s) used by libpng.  Currently, the only valid
     * value for "method" is 0.
     */
    PNG_EXPORT(67, void, png_set_filter, (png_structrp png_ptr, int method,
        int filters));

    /* Flags for png_set_filter() to say which filters to use.  The flags
     * are chosen so that they don't conflict with real filter types
     * below, in case they are supplied instead of the #defined constants.
     * These values should NOT be changed.
     */
    #define PNG_NO_FILTERS     0x00
    #define PNG_FILTER_NONE    0x08
    #define PNG_FILTER_SUB     0x10
    #define PNG_FILTER_UP      0x20
    #define PNG_FILTER_AVG     0x40
    #define PNG_FILTER_PAETH   0x80
    #define PNG_ALL_FILTERS (PNG_FILTER_NONE | PNG_FILTER_SUB | PNG_FILTER_UP | \
                             PNG_FILTER_AVG | PNG_FILTER_PAETH)

    /* Filter values (not flags) - used in pngwrite.c, pngwutil.c for now.
     * These defines should NOT be changed.
     */
    #define PNG_FILTER_VALUE_NONE  0
    #define PNG_FILTER_VALUE_SUB   1
    #define PNG_FILTER_VALUE_UP    2
    #define PNG_FILTER_VALUE_AVG   3
    #define PNG_FILTER_VALUE_PAETH 4
    #define PNG_FILTER_VALUE_LAST  5

    #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* EXPERIMENTAL */
    /* The "heuristic_method" is given by one of the PNG_FILTER_HEURISTIC_
     * defines, either the default (minimum-sum-of-absolute-differences), or
     * the experimental method (weighted-minimum-sum-of-absolute-differences).
     *
     * Weights are factors >= 1.0, indicating how important it is to keep the
     * filter type consistent between rows.  Larger numbers mean the current
     * filter is that many times as likely to be the same as the "num_weights"
     * previous filters.  This is cumulative for each previous row with a weight.
     * There needs to be "num_weights" values in "filter_weights", or it can be
     * NULL if the weights aren't being specified.  Weights have no influence on
     * the selection of the first row filter.  Well chosen weights can (in theory)
     * improve the compression for a given image.
     *
     * Costs are factors >= 1.0 indicating the relative decoding costs of a
     * filter type.  Higher costs indicate more decoding expense, and are
     * therefore less likely to be selected over a filter with lower computational
     * costs.  There needs to be a value in "filter_costs" for each valid filter
     * type (given by PNG_FILTER_VALUE_LAST), or it can be NULL if you aren't
     * setting the costs.  Costs try to improve the speed of decompression without
     * unduly increasing the compressed image size.
     *
     * A negative weight or cost indicates the default value is to be used, and
     * values in the range [0.0, 1.0) indicate the value is to remain unchanged.
     * The default values for both weights and costs are currently 1.0, but may
     * change if good general weighting/cost heuristics can be found.  If both
     * the weights and costs are set to 1.0, this degenerates the WEIGHTED method
     * to the UNWEIGHTED method, but with added encoding time/computation.
     */
    PNG_FP_EXPORT(68, void, png_set_filter_heuristics, (png_structrp png_ptr,
        int heuristic_method, int num_weights, png_const_doublep filter_weights,
        png_const_doublep filter_costs))
    PNG_FIXED_EXPORT(209, void, png_set_filter_heuristics_fixed,
        (png_structrp png_ptr, int heuristic_method, int num_weights,
        png_const_fixed_point_p filter_weights,
        png_const_fixed_point_p filter_costs))
    #endif /*  PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */

    /* Heuristic used for row filter selection.  These defines should NOT be
     * changed.
     */
    #define PNG_FILTER_HEURISTIC_DEFAULT    0  /* Currently "UNWEIGHTED" */
    #define PNG_FILTER_HEURISTIC_UNWEIGHTED 1  /* Used by libpng < 0.95 */
    #define PNG_FILTER_HEURISTIC_WEIGHTED   2  /* Experimental feature */
    #define PNG_FILTER_HEURISTIC_LAST       3  /* Not a valid value */

    #ifdef PNG_WRITE_SUPPORTED
    /* Set the library compression level.  Currently, valid values range from
     * 0 - 9, corresponding directly to the zlib compression levels 0 - 9
     * (0 - no compression, 9 - "maximal" compression).  Note that tests have
     * shown that zlib compression levels 3-6 usually perform as well as level 9
     * for PNG images, and do considerably fewer caclulations.  In the future,
     * these values may not correspond directly to the zlib compression levels.
     */
    PNG_EXPORT(69, void, png_set_compression_level, (png_structrp png_ptr,
        int level));

    PNG_EXPORT(70, void, png_set_compression_mem_level, (png_structrp png_ptr,
        int mem_level));

    PNG_EXPORT(71, void, png_set_compression_strategy, (png_structrp png_ptr,
        int strategy));

    /* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
     * smaller value of window_bits if it can do so safely.
     */
    PNG_EXPORT(72, void, png_set_compression_window_bits, (png_structrp png_ptr,
        int window_bits));

    PNG_EXPORT(73, void, png_set_compression_method, (png_structrp png_ptr,
        int method));
    #endif

    #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
    /* Also set zlib parameters for compressing non-IDAT chunks */
    PNG_EXPORT(222, void, png_set_text_compression_level, (png_structrp png_ptr,
        int level));

    PNG_EXPORT(223, void, png_set_text_compression_mem_level, (png_structrp png_ptr,
        int mem_level));

    PNG_EXPORT(224, void, png_set_text_compression_strategy, (png_structrp png_ptr,
        int strategy));

    /* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
     * smaller value of window_bits if it can do so safely.
     */
    PNG_EXPORT(225, void, png_set_text_compression_window_bits,
        (png_structrp png_ptr, int window_bits));

    PNG_EXPORT(226, void, png_set_text_compression_method, (png_structrp png_ptr,
        int method));
    #endif /* PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED */

    /* These next functions are called for input/output, memory, and error
     * handling.  They are in the file pngrio.c, pngwio.c, and pngerror.c,
     * and call standard C I/O routines such as fread(), fwrite(), and
     * fprintf().  These functions can be made to use other I/O routines
     * at run time for those applications that need to handle I/O in a
     * different manner by calling png_set_???_fn().  See libpng-manual.txt for
     * more information.
     */

    #ifdef PNG_STDIO_SUPPORTED
    /* Initialize the input/output for the PNG file to the default functions. */
    PNG_EXPORT(74, void, png_init_io, (png_structrp png_ptr, png_FILE_p fp));
    #endif

    /* Replace the (error and abort), and warning functions with user
     * supplied functions.  If no messages are to be printed you must still
     * write and use replacement functions. The replacement error_fn should
     * still do a longjmp to the last setjmp location if you are using this
     * method of error handling.  If error_fn or warning_fn is NULL, the
     * default function will be used.
     */

    PNG_EXPORT(75, void, png_set_error_fn, (png_structrp png_ptr,
        png_voidp error_ptr, png_error_ptr error_fn, png_error_ptr warning_fn));

    /* Return the user pointer associated with the error functions */
    PNG_EXPORT(76, png_voidp, png_get_error_ptr, (png_const_structrp png_ptr));

    /* Replace the default data output functions with a user supplied one(s).
     * If buffered output is not used, then output_flush_fn can be set to NULL.
     * If PNG_WRITE_FLUSH_SUPPORTED is not defined at libpng compile time
     * output_flush_fn will be ignored (and thus can be NULL).
     * It is probably a mistake to use NULL for output_flush_fn if
     * write_data_fn is not also NULL unless you have built libpng with
     * PNG_WRITE_FLUSH_SUPPORTED undefined, because in this case libpng's
     * default flush function, which uses the standard *FILE structure, will
     * be used.
     */
    PNG_EXPORT(77, void, png_set_write_fn, (png_structrp png_ptr, png_voidp io_ptr,
        png_rw_ptr write_data_fn, png_flush_ptr output_flush_fn));

    /* Replace the default data input function with a user supplied one. */
    PNG_EXPORT(78, void, png_set_read_fn, (png_structrp png_ptr, png_voidp io_ptr,
        png_rw_ptr read_data_fn));

    /* Return the user pointer associated with the I/O functions */
    PNG_EXPORT(79, png_voidp, png_get_io_ptr, (png_const_structrp png_ptr));

    PNG_EXPORT(80, void, png_set_read_status_fn, (png_structrp png_ptr,
        png_read_status_ptr read_row_fn));

    PNG_EXPORT(81, void, png_set_write_status_fn, (png_structrp png_ptr,
        png_write_status_ptr write_row_fn));

    #ifdef PNG_USER_MEM_SUPPORTED
    /* Replace the default memory allocation functions with user supplied one(s). */
    PNG_EXPORT(82, void, png_set_mem_fn, (png_structrp png_ptr, png_voidp mem_ptr,
        png_malloc_ptr malloc_fn, png_free_ptr free_fn));
    /* Return the user pointer associated with the memory functions */
    PNG_EXPORT(83, png_voidp, png_get_mem_ptr, (png_const_structrp png_ptr));
    #endif

    #ifdef PNG_READ_USER_TRANSFORM_SUPPORTED
    PNG_EXPORT(84, void, png_set_read_user_transform_fn, (png_structrp png_ptr,
        png_user_transform_ptr read_user_transform_fn));
    #endif

    #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
    PNG_EXPORT(85, void, png_set_write_user_transform_fn, (png_structrp png_ptr,
        png_user_transform_ptr write_user_transform_fn));
    #endif

    #ifdef PNG_USER_TRANSFORM_PTR_SUPPORTED
    PNG_EXPORT(86, void, png_set_user_transform_info, (png_structrp png_ptr,
        png_voidp user_transform_ptr, int user_transform_depth,
        int user_transform_channels));
    /* Return the user pointer associated with the user transform functions */
    PNG_EXPORT(87, png_voidp, png_get_user_transform_ptr,
        (png_const_structrp png_ptr));
    #endif

    #ifdef PNG_USER_TRANSFORM_INFO_SUPPORTED
    /* Return information about the row currently being processed.  Note that these
     * APIs do not fail but will return unexpected results if called outside a user
     * transform callback.  Also note that when transforming an interlaced image the
     * row number is the row number within the sub-image of the interlace pass, so
     * the value will increase to the height of the sub-image (not the full image)
     * then reset to 0 for the next pass.
     *
     * Use PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to
     * find the output pixel (x,y) given an interlaced sub-image pixel
     * (row,col,pass).  (See below for these macros.)
     */
    PNG_EXPORT(217, png_uint_32, png_get_current_row_number, (png_const_structrp));
    PNG_EXPORT(218, png_byte, png_get_current_pass_number, (png_const_structrp));
    #endif

    #ifdef PNG_READ_USER_CHUNKS_SUPPORTED
    /* This callback is called only for *unknown* chunks.  If
     * PNG_HANDLE_AS_UNKNOWN_SUPPORTED is set then it is possible to set known
     * chunks to be treated as unknown, however in this case the callback must do
     * any processing required by the chunk (e.g. by calling the appropriate
     * png_set_ APIs.)
     *
     * There is no write support - on write, by default, all the chunks in the
     * 'unknown' list are written in the specified position.
     *
     * The integer return from the callback function is interpreted thus:
     *
     * negative: An error occured, png_chunk_error will be called.
     *     zero: The chunk was not handled, the chunk will be saved. A critical
     *           chunk will cause an error at this point unless it is to be saved.
     * positive: The chunk was handled, libpng will ignore/discard it.
     *
     * See "INTERACTION WTIH USER CHUNK CALLBACKS" below for important notes about
     * how this behavior will change in libpng 1.7
     */
    PNG_EXPORT(88, void, png_set_read_user_chunk_fn, (png_structrp png_ptr,
        png_voidp user_chunk_ptr, png_user_chunk_ptr read_user_chunk_fn));
    #endif

    #ifdef PNG_USER_CHUNKS_SUPPORTED
    PNG_EXPORT(89, png_voidp, png_get_user_chunk_ptr, (png_const_structrp png_ptr));
    #endif

    #ifdef PNG_PROGRESSIVE_READ_SUPPORTED
    /* Sets the function callbacks for the push reader, and a pointer to a
     * user-defined structure available to the callback functions.
     */
    PNG_EXPORT(90, void, png_set_progressive_read_fn, (png_structrp png_ptr,
        png_voidp progressive_ptr, png_progressive_info_ptr info_fn,
        png_progressive_row_ptr row_fn, png_progressive_end_ptr end_fn));

    /* Returns the user pointer associated with the push read functions */
    PNG_EXPORT(91, png_voidp, png_get_progressive_ptr,
        (png_const_structrp png_ptr));

    /* Function to be called when data becomes available */
    PNG_EXPORT(92, void, png_process_data, (png_structrp png_ptr,
        png_inforp info_ptr, png_bytep buffer, png_size_t buffer_size));

    /* A function which may be called *only* within png_process_data to stop the
     * processing of any more data.  The function returns the number of bytes
     * remaining, excluding any that libpng has cached internally.  A subsequent
     * call to png_process_data must supply these bytes again.  If the argument
     * 'save' is set to true the routine will first save all the pending data and
     * will always return 0.
     */
    PNG_EXPORT(219, png_size_t, png_process_data_pause, (png_structrp, int save));

    /* A function which may be called *only* outside (after) a call to
     * png_process_data.  It returns the number of bytes of data to skip in the
     * input.  Normally it will return 0, but if it returns a non-zero value the
     * application must skip than number of bytes of input data and pass the
     * following data to the next call to png_process_data.
     */
    PNG_EXPORT(220, png_uint_32, png_process_data_skip, (png_structrp));

    #ifdef PNG_READ_INTERLACING_SUPPORTED
    /* Function that combines rows.  'new_row' is a flag that should come from
     * the callback and be non-NULL if anything needs to be done; the library
     * stores its own version of the new data internally and ignores the passed
     * in value.
     */
    PNG_EXPORT(93, void, png_progressive_combine_row, (png_const_structrp png_ptr,
        png_bytep old_row, png_const_bytep new_row));
    #endif /* PNG_READ_INTERLACING_SUPPORTED */
    #endif /* PNG_PROGRESSIVE_READ_SUPPORTED */

    PNG_EXPORTA(94, png_voidp, png_malloc, (png_const_structrp png_ptr,
        png_alloc_size_t size), PNG_ALLOCATED);
    /* Added at libpng version 1.4.0 */
    PNG_EXPORTA(95, png_voidp, png_calloc, (png_const_structrp png_ptr,
        png_alloc_size_t size), PNG_ALLOCATED);

    /* Added at libpng version 1.2.4 */
    PNG_EXPORTA(96, png_voidp, png_malloc_warn, (png_const_structrp png_ptr,
        png_alloc_size_t size), PNG_ALLOCATED);

    /* Frees a pointer allocated by png_malloc() */
    PNG_EXPORT(97, void, png_free, (png_const_structrp png_ptr, png_voidp ptr));

    /* Free data that was allocated internally */
    PNG_EXPORT(98, void, png_free_data, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_uint_32 free_me, int num));

    /* Reassign responsibility for freeing existing data, whether allocated
     * by libpng or by the application; this works on the png_info structure passed
     * in, it does not change the state for other png_info structures.
     *
     * It is unlikely that this function works correctly as of 1.6.0 and using it
     * may result either in memory leaks or double free of allocated data.
     */
    PNG_EXPORTA(99, void, png_data_freer, (png_const_structrp png_ptr,
        png_inforp info_ptr, int freer, png_uint_32 mask), PNG_DEPRECATED);

    /* Assignments for png_data_freer */
    #define PNG_DESTROY_WILL_FREE_DATA 1
    #define PNG_SET_WILL_FREE_DATA 1
    #define PNG_USER_WILL_FREE_DATA 2
    /* Flags for png_ptr->free_me and info_ptr->free_me */
    #define PNG_FREE_HIST 0x0008
    #define PNG_FREE_ICCP 0x0010
    #define PNG_FREE_SPLT 0x0020
    #define PNG_FREE_ROWS 0x0040
    #define PNG_FREE_PCAL 0x0080
    #define PNG_FREE_SCAL 0x0100
    #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
    #  define PNG_FREE_UNKN 0x0200
    #endif
    /*      PNG_FREE_LIST 0x0400    removed in 1.6.0 because it is ignored */
    #define PNG_FREE_PLTE 0x1000
    #define PNG_FREE_TRNS 0x2000
    #define PNG_FREE_TEXT 0x4000
    #define PNG_FREE_ALL  0x7fff
    #define PNG_FREE_MUL  0x4220 /* PNG_FREE_SPLT|PNG_FREE_TEXT|PNG_FREE_UNKN */

    #ifdef PNG_USER_MEM_SUPPORTED
    PNG_EXPORTA(100, png_voidp, png_malloc_default, (png_const_structrp png_ptr,
        png_alloc_size_t size), PNG_ALLOCATED PNG_DEPRECATED);
    PNG_EXPORTA(101, void, png_free_default, (png_const_structrp png_ptr,
        png_voidp ptr), PNG_DEPRECATED);
    #endif

    #ifdef PNG_ERROR_TEXT_SUPPORTED
    /* Fatal error in PNG image of libpng - can't continue */
    PNG_EXPORTA(102, void, png_error, (png_const_structrp png_ptr,
        png_const_charp error_message), PNG_NORETURN);

    /* The same, but the chunk name is prepended to the error string. */
    PNG_EXPORTA(103, void, png_chunk_error, (png_const_structrp png_ptr,
        png_const_charp error_message), PNG_NORETURN);

    #else
    /* Fatal error in PNG image of libpng - can't continue */
    PNG_EXPORTA(104, void, png_err, (png_const_structrp png_ptr), PNG_NORETURN);
    #endif

    #ifdef PNG_WARNINGS_SUPPORTED
    /* Non-fatal error in libpng.  Can continue, but may have a problem. */
    PNG_EXPORT(105, void, png_warning, (png_const_structrp png_ptr,
        png_const_charp warning_message));

    /* Non-fatal error in libpng, chunk name is prepended to message. */
    PNG_EXPORT(106, void, png_chunk_warning, (png_const_structrp png_ptr,
        png_const_charp warning_message));
    #endif

    #ifdef PNG_BENIGN_ERRORS_SUPPORTED
    /* Benign error in libpng.  Can continue, but may have a problem.
     * User can choose whether to handle as a fatal error or as a warning. */
    PNG_EXPORT(107, void, png_benign_error, (png_const_structrp png_ptr,
        png_const_charp warning_message));

    #ifdef PNG_READ_SUPPORTED
    /* Same, chunk name is prepended to message (only during read) */
    PNG_EXPORT(108, void, png_chunk_benign_error, (png_const_structrp png_ptr,
        png_const_charp warning_message));
    #endif

    PNG_EXPORT(109, void, png_set_benign_errors,
        (png_structrp png_ptr, int allowed));
    #else
    #  ifdef PNG_ALLOW_BENIGN_ERRORS
    #    define png_benign_error png_warning
    #    define png_chunk_benign_error png_chunk_warning
    #  else
    #    define png_benign_error png_error
    #    define png_chunk_benign_error png_chunk_error
    #  endif
    #endif

    /* The png_set_<chunk> functions are for storing values in the png_info_struct.
     * Similarly, the png_get_<chunk> calls are used to read values from the
     * png_info_struct, either storing the parameters in the passed variables, or
     * setting pointers into the png_info_struct where the data is stored.  The
     * png_get_<chunk> functions return a non-zero value if the data was available
     * in info_ptr, or return zero and do not change any of the parameters if the
     * data was not available.
     *
     * These functions should be used instead of directly accessing png_info
     * to avoid problems with future changes in the size and internal layout of
     * png_info_struct.
     */
    /* Returns "flag" if chunk data is valid in info_ptr. */
    PNG_EXPORT(110, png_uint_32, png_get_valid, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, png_uint_32 flag));

    /* Returns number of bytes needed to hold a transformed row. */
    PNG_EXPORT(111, png_size_t, png_get_rowbytes, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    #ifdef PNG_INFO_IMAGE_SUPPORTED
    /* Returns row_pointers, which is an array of pointers to scanlines that was
     * returned from png_read_png().
     */
    PNG_EXPORT(112, png_bytepp, png_get_rows, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Set row_pointers, which is an array of pointers to scanlines for use
     * by png_write_png().
     */
    PNG_EXPORT(113, void, png_set_rows, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_bytepp row_pointers));
    #endif

    /* Returns number of color channels in image. */
    PNG_EXPORT(114, png_byte, png_get_channels, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    #ifdef PNG_EASY_ACCESS_SUPPORTED
    /* Returns image width in pixels. */
    PNG_EXPORT(115, png_uint_32, png_get_image_width, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image height in pixels. */
    PNG_EXPORT(116, png_uint_32, png_get_image_height, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image bit_depth. */
    PNG_EXPORT(117, png_byte, png_get_bit_depth, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image color_type. */
    PNG_EXPORT(118, png_byte, png_get_color_type, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image filter_type. */
    PNG_EXPORT(119, png_byte, png_get_filter_type, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image interlace_type. */
    PNG_EXPORT(120, png_byte, png_get_interlace_type, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image compression_type. */
    PNG_EXPORT(121, png_byte, png_get_compression_type, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));

    /* Returns image resolution in pixels per meter, from pHYs chunk data. */
    PNG_EXPORT(122, png_uint_32, png_get_pixels_per_meter,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(123, png_uint_32, png_get_x_pixels_per_meter,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(124, png_uint_32, png_get_y_pixels_per_meter,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));

    /* Returns pixel aspect ratio, computed from pHYs chunk data.  */
    PNG_FP_EXPORT(125, float, png_get_pixel_aspect_ratio,
        (png_const_structrp png_ptr, png_const_inforp info_ptr))
    PNG_FIXED_EXPORT(210, png_fixed_point, png_get_pixel_aspect_ratio_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr))

    /* Returns image x, y offset in pixels or microns, from oFFs chunk data. */
    PNG_EXPORT(126, png_int_32, png_get_x_offset_pixels,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(127, png_int_32, png_get_y_offset_pixels,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(128, png_int_32, png_get_x_offset_microns,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));
    PNG_EXPORT(129, png_int_32, png_get_y_offset_microns,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));

    #endif /* PNG_EASY_ACCESS_SUPPORTED */

    #ifdef PNG_READ_SUPPORTED
    /* Returns pointer to signature string read from PNG header */
    PNG_EXPORT(130, png_const_bytep, png_get_signature, (png_const_structrp png_ptr,
        png_const_inforp info_ptr));
    #endif

    #ifdef PNG_bKGD_SUPPORTED
    PNG_EXPORT(131, png_uint_32, png_get_bKGD, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_color_16p *background));
    #endif

    #ifdef PNG_bKGD_SUPPORTED
    PNG_EXPORT(132, void, png_set_bKGD, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_color_16p background));
    #endif

    #ifdef PNG_cHRM_SUPPORTED
    PNG_FP_EXPORT(133, png_uint_32, png_get_cHRM, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, double *white_x, double *white_y, double *red_x,
        double *red_y, double *green_x, double *green_y, double *blue_x,
        double *blue_y))
    PNG_FP_EXPORT(230, png_uint_32, png_get_cHRM_XYZ, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, double *red_X, double *red_Y, double *red_Z,
        double *green_X, double *green_Y, double *green_Z, double *blue_X,
        double *blue_Y, double *blue_Z))
    PNG_FIXED_EXPORT(134, png_uint_32, png_get_cHRM_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr,
        png_fixed_point *int_white_x, png_fixed_point *int_white_y,
        png_fixed_point *int_red_x, png_fixed_point *int_red_y,
        png_fixed_point *int_green_x, png_fixed_point *int_green_y,
        png_fixed_point *int_blue_x, png_fixed_point *int_blue_y))
    PNG_FIXED_EXPORT(231, png_uint_32, png_get_cHRM_XYZ_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr,
        png_fixed_point *int_red_X, png_fixed_point *int_red_Y,
        png_fixed_point *int_red_Z, png_fixed_point *int_green_X,
        png_fixed_point *int_green_Y, png_fixed_point *int_green_Z,
        png_fixed_point *int_blue_X, png_fixed_point *int_blue_Y,
        png_fixed_point *int_blue_Z))
    #endif

    #ifdef PNG_cHRM_SUPPORTED
    PNG_FP_EXPORT(135, void, png_set_cHRM, (png_const_structrp png_ptr,
        png_inforp info_ptr,
        double white_x, double white_y, double red_x, double red_y, double green_x,
        double green_y, double blue_x, double blue_y))
    PNG_FP_EXPORT(232, void, png_set_cHRM_XYZ, (png_const_structrp png_ptr,
        png_inforp info_ptr, double red_X, double red_Y, double red_Z,
        double green_X, double green_Y, double green_Z, double blue_X,
        double blue_Y, double blue_Z))
    PNG_FIXED_EXPORT(136, void, png_set_cHRM_fixed, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_fixed_point int_white_x,
        png_fixed_point int_white_y, png_fixed_point int_red_x,
        png_fixed_point int_red_y, png_fixed_point int_green_x,
        png_fixed_point int_green_y, png_fixed_point int_blue_x,
        png_fixed_point int_blue_y))
    PNG_FIXED_EXPORT(233, void, png_set_cHRM_XYZ_fixed, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_fixed_point int_red_X, png_fixed_point int_red_Y,
        png_fixed_point int_red_Z, png_fixed_point int_green_X,
        png_fixed_point int_green_Y, png_fixed_point int_green_Z,
        png_fixed_point int_blue_X, png_fixed_point int_blue_Y,
        png_fixed_point int_blue_Z))
    #endif

    #ifdef PNG_gAMA_SUPPORTED
    PNG_FP_EXPORT(137, png_uint_32, png_get_gAMA, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, double *file_gamma))
    PNG_FIXED_EXPORT(138, png_uint_32, png_get_gAMA_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr,
        png_fixed_point *int_file_gamma))
    #endif

    #ifdef PNG_gAMA_SUPPORTED
    PNG_FP_EXPORT(139, void, png_set_gAMA, (png_const_structrp png_ptr,
        png_inforp info_ptr, double file_gamma))
    PNG_FIXED_EXPORT(140, void, png_set_gAMA_fixed, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_fixed_point int_file_gamma))
    #endif

    #ifdef PNG_hIST_SUPPORTED
    PNG_EXPORT(141, png_uint_32, png_get_hIST, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_uint_16p *hist));
    #endif

    #ifdef PNG_hIST_SUPPORTED
    PNG_EXPORT(142, void, png_set_hIST, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_uint_16p hist));
    #endif

    PNG_EXPORT(143, png_uint_32, png_get_IHDR, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, png_uint_32 *width, png_uint_32 *height,
        int *bit_depth, int *color_type, int *interlace_method,
        int *compression_method, int *filter_method));

    PNG_EXPORT(144, void, png_set_IHDR, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_uint_32 width, png_uint_32 height, int bit_depth,
        int color_type, int interlace_method, int compression_method,
        int filter_method));

    #ifdef PNG_oFFs_SUPPORTED
    PNG_EXPORT(145, png_uint_32, png_get_oFFs, (png_const_structrp png_ptr,
       png_const_inforp info_ptr, png_int_32 *offset_x, png_int_32 *offset_y,
       int *unit_type));
    #endif

    #ifdef PNG_oFFs_SUPPORTED
    PNG_EXPORT(146, void, png_set_oFFs, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_int_32 offset_x, png_int_32 offset_y,
        int unit_type));
    #endif

    #ifdef PNG_pCAL_SUPPORTED
    PNG_EXPORT(147, png_uint_32, png_get_pCAL, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_charp *purpose, png_int_32 *X0,
        png_int_32 *X1, int *type, int *nparams, png_charp *units,
        png_charpp *params));
    #endif

    #ifdef PNG_pCAL_SUPPORTED
    PNG_EXPORT(148, void, png_set_pCAL, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_charp purpose, png_int_32 X0, png_int_32 X1,
        int type, int nparams, png_const_charp units, png_charpp params));
    #endif

    #ifdef PNG_pHYs_SUPPORTED
    PNG_EXPORT(149, png_uint_32, png_get_pHYs, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, png_uint_32 *res_x, png_uint_32 *res_y,
        int *unit_type));
    #endif

    #ifdef PNG_pHYs_SUPPORTED
    PNG_EXPORT(150, void, png_set_pHYs, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_uint_32 res_x, png_uint_32 res_y, int unit_type));
    #endif

    PNG_EXPORT(151, png_uint_32, png_get_PLTE, (png_const_structrp png_ptr,
       png_inforp info_ptr, png_colorp *palette, int *num_palette));

    PNG_EXPORT(152, void, png_set_PLTE, (png_structrp png_ptr,
        png_inforp info_ptr, png_const_colorp palette, int num_palette));

    #ifdef PNG_sBIT_SUPPORTED
    PNG_EXPORT(153, png_uint_32, png_get_sBIT, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_color_8p *sig_bit));
    #endif

    #ifdef PNG_sBIT_SUPPORTED
    PNG_EXPORT(154, void, png_set_sBIT, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_color_8p sig_bit));
    #endif

    #ifdef PNG_sRGB_SUPPORTED
    PNG_EXPORT(155, png_uint_32, png_get_sRGB, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, int *file_srgb_intent));
    #endif

    #ifdef PNG_sRGB_SUPPORTED
    PNG_EXPORT(156, void, png_set_sRGB, (png_const_structrp png_ptr,
        png_inforp info_ptr, int srgb_intent));
    PNG_EXPORT(157, void, png_set_sRGB_gAMA_and_cHRM, (png_const_structrp png_ptr,
        png_inforp info_ptr, int srgb_intent));
    #endif

    #ifdef PNG_iCCP_SUPPORTED
    PNG_EXPORT(158, png_uint_32, png_get_iCCP, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_charpp name, int *compression_type,
        png_bytepp profile, png_uint_32 *proflen));
    #endif

    #ifdef PNG_iCCP_SUPPORTED
    PNG_EXPORT(159, void, png_set_iCCP, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_charp name, int compression_type,
        png_const_bytep profile, png_uint_32 proflen));
    #endif

    #ifdef PNG_sPLT_SUPPORTED
    PNG_EXPORT(160, int, png_get_sPLT, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_sPLT_tpp entries));
    #endif

    #ifdef PNG_sPLT_SUPPORTED
    PNG_EXPORT(161, void, png_set_sPLT, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_sPLT_tp entries, int nentries));
    #endif

    #ifdef PNG_TEXT_SUPPORTED
    /* png_get_text also returns the number of text chunks in *num_text */
    PNG_EXPORT(162, int, png_get_text, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_textp *text_ptr, int *num_text));
    #endif

    /* Note while png_set_text() will accept a structure whose text,
     * language, and  translated keywords are NULL pointers, the structure
     * returned by png_get_text will always contain regular
     * zero-terminated C strings.  They might be empty strings but
     * they will never be NULL pointers.
     */

    #ifdef PNG_TEXT_SUPPORTED
    PNG_EXPORT(163, void, png_set_text, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_textp text_ptr, int num_text));
    #endif

    #ifdef PNG_tIME_SUPPORTED
    PNG_EXPORT(164, png_uint_32, png_get_tIME, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_timep *mod_time));
    #endif

    #ifdef PNG_tIME_SUPPORTED
    PNG_EXPORT(165, void, png_set_tIME, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_timep mod_time));
    #endif

    #ifdef PNG_tRNS_SUPPORTED
    PNG_EXPORT(166, png_uint_32, png_get_tRNS, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_bytep *trans_alpha, int *num_trans,
        png_color_16p *trans_color));
    #endif

    #ifdef PNG_tRNS_SUPPORTED
    PNG_EXPORT(167, void, png_set_tRNS, (png_structrp png_ptr,
        png_inforp info_ptr, png_const_bytep trans_alpha, int num_trans,
        png_const_color_16p trans_color));
    #endif

    #ifdef PNG_sCAL_SUPPORTED
    PNG_FP_EXPORT(168, png_uint_32, png_get_sCAL, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, int *unit, double *width, double *height))
    #if defined(PNG_FLOATING_ARITHMETIC_SUPPORTED) || \
       defined(PNG_FLOATING_POINT_SUPPORTED)
    /* NOTE: this API is currently implemented using floating point arithmetic,
     * consequently it can only be used on systems with floating point support.
     * In any case the range of values supported by png_fixed_point is small and it
     * is highly recommended that png_get_sCAL_s be used instead.
     */
    PNG_FIXED_EXPORT(214, png_uint_32, png_get_sCAL_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr, int *unit,
        png_fixed_point *width, png_fixed_point *height))
    #endif
    PNG_EXPORT(169, png_uint_32, png_get_sCAL_s,
        (png_const_structrp png_ptr, png_const_inforp info_ptr, int *unit,
        png_charpp swidth, png_charpp sheight));

    PNG_FP_EXPORT(170, void, png_set_sCAL, (png_const_structrp png_ptr,
        png_inforp info_ptr, int unit, double width, double height))
    PNG_FIXED_EXPORT(213, void, png_set_sCAL_fixed, (png_const_structrp png_ptr,
       png_inforp info_ptr, int unit, png_fixed_point width,
       png_fixed_point height))
    PNG_EXPORT(171, void, png_set_sCAL_s, (png_const_structrp png_ptr,
        png_inforp info_ptr, int unit,
        png_const_charp swidth, png_const_charp sheight));
    #endif /* PNG_sCAL_SUPPORTED */

    #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
    /* Provide the default handling for all unknown chunks or, optionally, for
     * specific unknown chunks.
     *
     * NOTE: prior to 1.6.0 the handling specified for particular chunks on read was
     * ignored and the default was used, the per-chunk setting only had an effect on
     * write.  If you wish to have chunk-specific handling on read in code that must
     * work on earlier versions you must use a user chunk callback to specify the
     * desired handling (keep or discard.)
     *
     * The 'keep' parameter is a PNG_HANDLE_CHUNK_ value as listed below.  The
     * parameter is interpreted as follows:
     *
     * READ:
     *    PNG_HANDLE_CHUNK_AS_DEFAULT:
     *       Known chunks: do normal libpng processing, do not keep the chunk (but
     *          see the comments below about PNG_HANDLE_AS_UNKNOWN_SUPPORTED)
     *       Unknown chunks: for a specific chunk use the global default, when used
     *          as the default discard the chunk data.
     *    PNG_HANDLE_CHUNK_NEVER:
     *       Discard the chunk data.
     *    PNG_HANDLE_CHUNK_IF_SAFE:
     *       Keep the chunk data if the chunk is not critical else raise a chunk
     *       error.
     *    PNG_HANDLE_CHUNK_ALWAYS:
     *       Keep the chunk data.
     *
     * If the chunk data is saved it can be retrieved using png_get_unknown_chunks,
     * below.  Notice that specifying "AS_DEFAULT" as a global default is equivalent
     * to specifying "NEVER", however when "AS_DEFAULT" is used for specific chunks
     * it simply resets the behavior to the libpng default.
     *
     * INTERACTION WTIH USER CHUNK CALLBACKS:
     * The per-chunk handling is always used when there is a png_user_chunk_ptr
     * callback and the callback returns 0; the chunk is then always stored *unless*
     * it is critical and the per-chunk setting is other than ALWAYS.  Notice that
     * the global default is *not* used in this case.  (In effect the per-chunk
     * value is incremented to at least IF_SAFE.)
     *
     * IMPORTANT NOTE: this behavior will change in libpng 1.7 - the global and
     * per-chunk defaults will be honored.  If you want to preserve the current
     * behavior when your callback returns 0 you must set PNG_HANDLE_CHUNK_IF_SAFE
     * as the default - if you don't do this libpng 1.6 will issue a warning.
     *
     * If you want unhandled unknown chunks to be discarded in libpng 1.6 and
     * earlier simply return '1' (handled).
     *
     * PNG_HANDLE_AS_UNKNOWN_SUPPORTED:
     *    If this is *not* set known chunks will always be handled by libpng and
     *    will never be stored in the unknown chunk list.  Known chunks listed to
     *    png_set_keep_unknown_chunks will have no effect.  If it is set then known
     *    chunks listed with a keep other than AS_DEFAULT will *never* be processed
     *    by libpng, in addition critical chunks must either be processed by the
     *    callback or saved.
     *
     *    The IHDR and IEND chunks must not be listed.  Because this turns off the
     *    default handling for chunks that would otherwise be recognized the
     *    behavior of libpng transformations may well become incorrect!
     *
     * WRITE:
     *    When writing chunks the options only apply to the chunks specified by
     *    png_set_unknown_chunks (below), libpng will *always* write known chunks
     *    required by png_set_ calls and will always write the core critical chunks
     *    (as required for PLTE).
     *
     *    Each chunk in the png_set_unknown_chunks list is looked up in the
     *    png_set_keep_unknown_chunks list to find the keep setting, this is then
     *    interpreted as follows:
     *
     *    PNG_HANDLE_CHUNK_AS_DEFAULT:
     *       Write safe-to-copy chunks and write other chunks if the global
     *       default is set to _ALWAYS, otherwise don't write this chunk.
     *    PNG_HANDLE_CHUNK_NEVER:
     *       Do not write the chunk.
     *    PNG_HANDLE_CHUNK_IF_SAFE:
     *       Write the chunk if it is safe-to-copy, otherwise do not write it.
     *    PNG_HANDLE_CHUNK_ALWAYS:
     *       Write the chunk.
     *
     * Note that the default behavior is effectively the opposite of the read case -
     * in read unknown chunks are not stored by default, in write they are written
     * by default.  Also the behavior of PNG_HANDLE_CHUNK_IF_SAFE is very different
     * - on write the safe-to-copy bit is checked, on read the critical bit is
     * checked and on read if the chunk is critical an error will be raised.
     *
     * num_chunks:
     * ===========
     *    If num_chunks is positive, then the "keep" parameter specifies the manner
     *    for handling only those chunks appearing in the chunk_list array,
     *    otherwise the chunk list array is ignored.
     *
     *    If num_chunks is 0 the "keep" parameter specifies the default behavior for
     *    unknown chunks, as described above.
     *
     *    If num_chunks is negative, then the "keep" parameter specifies the manner
     *    for handling all unknown chunks plus all chunks recognized by libpng
     *    except for the IHDR, PLTE, tRNS, IDAT, and IEND chunks (which continue to
     *    be processed by libpng.
     */
    PNG_EXPORT(172, void, png_set_keep_unknown_chunks, (png_structrp png_ptr,
        int keep, png_const_bytep chunk_list, int num_chunks));

    /* The "keep" PNG_HANDLE_CHUNK_ parameter for the specified chunk is returned;
     * the result is therefore true (non-zero) if special handling is required,
     * false for the default handling.
     */
    PNG_EXPORT(173, int, png_handle_as_unknown, (png_const_structrp png_ptr,
        png_const_bytep chunk_name));
    #endif

    #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
    PNG_EXPORT(174, void, png_set_unknown_chunks, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_const_unknown_chunkp unknowns,
        int num_unknowns));
       /* NOTE: prior to 1.6.0 this routine set the 'location' field of the added
        * unknowns to the location currently stored in the png_struct.  This is
        * invariably the wrong value on write.  To fix this call the following API
        * for each chunk in the list with the correct location.  If you know your
        * code won't be compiled on earlier versions you can rely on
        * png_set_unknown_chunks(write-ptr, png_get_unknown_chunks(read-ptr)) doing
        * the correct thing.
        */

    PNG_EXPORT(175, void, png_set_unknown_chunk_location,
        (png_const_structrp png_ptr, png_inforp info_ptr, int chunk, int location));

    PNG_EXPORT(176, int, png_get_unknown_chunks, (png_const_structrp png_ptr,
        png_inforp info_ptr, png_unknown_chunkpp entries));
    #endif

    /* Png_free_data() will turn off the "valid" flag for anything it frees.
     * If you need to turn it off for a chunk that your application has freed,
     * you can use png_set_invalid(png_ptr, info_ptr, PNG_INFO_CHNK);
     */
    PNG_EXPORT(177, void, png_set_invalid, (png_const_structrp png_ptr,
        png_inforp info_ptr, int mask));

    #ifdef PNG_INFO_IMAGE_SUPPORTED
    /* The "params" pointer is currently not used and is for future expansion. */
    PNG_EXPORT(178, void, png_read_png, (png_structrp png_ptr, png_inforp info_ptr,
        int transforms, png_voidp params));
    PNG_EXPORT(179, void, png_write_png, (png_structrp png_ptr, png_inforp info_ptr,
        int transforms, png_voidp params));
    #endif

    PNG_EXPORT(180, png_const_charp, png_get_copyright,
        (png_const_structrp png_ptr));
    PNG_EXPORT(181, png_const_charp, png_get_header_ver,
        (png_const_structrp png_ptr));
    PNG_EXPORT(182, png_const_charp, png_get_header_version,
        (png_const_structrp png_ptr));
    PNG_EXPORT(183, png_const_charp, png_get_libpng_ver,
        (png_const_structrp png_ptr));

    #ifdef PNG_MNG_FEATURES_SUPPORTED
    PNG_EXPORT(184, png_uint_32, png_permit_mng_features, (png_structrp png_ptr,
        png_uint_32 mng_features_permitted));
    #endif

    /* For use in png_set_keep_unknown, added to version 1.2.6 */
    #define PNG_HANDLE_CHUNK_AS_DEFAULT   0
    #define PNG_HANDLE_CHUNK_NEVER        1
    #define PNG_HANDLE_CHUNK_IF_SAFE      2
    #define PNG_HANDLE_CHUNK_ALWAYS       3
    #define PNG_HANDLE_CHUNK_LAST         4

    /* Strip the prepended error numbers ("#nnn ") from error and warning
     * messages before passing them to the error or warning handler.
     */
    #ifdef PNG_ERROR_NUMBERS_SUPPORTED
    PNG_EXPORT(185, void, png_set_strip_error_numbers, (png_structrp png_ptr,
        png_uint_32 strip_mode));
    #endif

    /* Added in libpng-1.2.6 */
    #ifdef PNG_SET_USER_LIMITS_SUPPORTED
    PNG_EXPORT(186, void, png_set_user_limits, (png_structrp png_ptr,
        png_uint_32 user_width_max, png_uint_32 user_height_max));
    PNG_EXPORT(187, png_uint_32, png_get_user_width_max,
        (png_const_structrp png_ptr));
    PNG_EXPORT(188, png_uint_32, png_get_user_height_max,
        (png_const_structrp png_ptr));
    /* Added in libpng-1.4.0 */
    PNG_EXPORT(189, void, png_set_chunk_cache_max, (png_structrp png_ptr,
        png_uint_32 user_chunk_cache_max));
    PNG_EXPORT(190, png_uint_32, png_get_chunk_cache_max,
        (png_const_structrp png_ptr));
    /* Added in libpng-1.4.1 */
    PNG_EXPORT(191, void, png_set_chunk_malloc_max, (png_structrp png_ptr,
        png_alloc_size_t user_chunk_cache_max));
    PNG_EXPORT(192, png_alloc_size_t, png_get_chunk_malloc_max,
        (png_const_structrp png_ptr));
    #endif

    #if defined(PNG_INCH_CONVERSIONS_SUPPORTED)
    PNG_EXPORT(193, png_uint_32, png_get_pixels_per_inch,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));

    PNG_EXPORT(194, png_uint_32, png_get_x_pixels_per_inch,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));

    PNG_EXPORT(195, png_uint_32, png_get_y_pixels_per_inch,
        (png_const_structrp png_ptr, png_const_inforp info_ptr));

    PNG_FP_EXPORT(196, float, png_get_x_offset_inches,
        (png_const_structrp png_ptr, png_const_inforp info_ptr))
    #ifdef PNG_FIXED_POINT_SUPPORTED /* otherwise not implemented. */
    PNG_FIXED_EXPORT(211, png_fixed_point, png_get_x_offset_inches_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr))
    #endif

    PNG_FP_EXPORT(197, float, png_get_y_offset_inches, (png_const_structrp png_ptr,
        png_const_inforp info_ptr))
    #ifdef PNG_FIXED_POINT_SUPPORTED /* otherwise not implemented. */
    PNG_FIXED_EXPORT(212, png_fixed_point, png_get_y_offset_inches_fixed,
        (png_const_structrp png_ptr, png_const_inforp info_ptr))
    #endif

    #  ifdef PNG_pHYs_SUPPORTED
    PNG_EXPORT(198, png_uint_32, png_get_pHYs_dpi, (png_const_structrp png_ptr,
        png_const_inforp info_ptr, png_uint_32 *res_x, png_uint_32 *res_y,
        int *unit_type));
    #  endif /* PNG_pHYs_SUPPORTED */
    #endif  /* PNG_INCH_CONVERSIONS_SUPPORTED */

    /* Added in libpng-1.4.0 */
    #ifdef PNG_IO_STATE_SUPPORTED
    PNG_EXPORT(199, png_uint_32, png_get_io_state, (png_const_structrp png_ptr));

    /* Removed from libpng 1.6; use png_get_io_chunk_type. */
    PNG_REMOVED(200, png_const_bytep, png_get_io_chunk_name, (png_structrp png_ptr),
        PNG_DEPRECATED)

    PNG_EXPORT(216, png_uint_32, png_get_io_chunk_type,
        (png_const_structrp png_ptr));

    /* The flags returned by png_get_io_state() are the following: */
    #  define PNG_IO_NONE        0x0000   /* no I/O at this moment */
    #  define PNG_IO_READING     0x0001   /* currently reading */
    #  define PNG_IO_WRITING     0x0002   /* currently writing */
    #  define PNG_IO_SIGNATURE   0x0010   /* currently at the file signature */
    #  define PNG_IO_CHUNK_HDR   0x0020   /* currently at the chunk header */
    #  define PNG_IO_CHUNK_DATA  0x0040   /* currently at the chunk data */
    #  define PNG_IO_CHUNK_CRC   0x0080   /* currently at the chunk crc */
    #  define PNG_IO_MASK_OP     0x000f   /* current operation: reading/writing */
    #  define PNG_IO_MASK_LOC    0x00f0   /* current location: sig/hdr/data/crc */
    #endif /* ?PNG_IO_STATE_SUPPORTED */

    /* Interlace support.  The following macros are always defined so that if
     * libpng interlace handling is turned off the macros may be used to handle
     * interlaced images within the application.
     */
    #define PNG_INTERLACE_ADAM7_PASSES 7

    /* Two macros to return the first row and first column of the original,
     * full, image which appears in a given pass.  'pass' is in the range 0
     * to 6 and the result is in the range 0 to 7.
     */
    #define PNG_PASS_START_ROW(pass) (((1&~(pass))<<(3-((pass)>>1)))&7)
    #define PNG_PASS_START_COL(pass) (((1& (pass))<<(3-(((pass)+1)>>1)))&7)

    /* A macro to return the offset between pixels in the output row for a pair of
     * pixels in the input - effectively the inverse of the 'COL_SHIFT' macro that
     * follows.  Note that ROW_OFFSET is the offset from one row to the next whereas
     * COL_OFFSET is from one column to the next, within a row.
     */
    #define PNG_PASS_ROW_OFFSET(pass) ((pass)>2?(8>>(((pass)-1)>>1)):8)
    #define PNG_PASS_COL_OFFSET(pass) (1<<((7-(pass))>>1))

    /* Two macros to help evaluate the number of rows or columns in each
     * pass.  This is expressed as a shift - effectively log2 of the number or
     * rows or columns in each 8x8 tile of the original image.
     */
    #define PNG_PASS_ROW_SHIFT(pass) ((pass)>2?(8-(pass))>>1:3)
    #define PNG_PASS_COL_SHIFT(pass) ((pass)>1?(7-(pass))>>1:3)

    /* Hence two macros to determine the number of rows or columns in a given
     * pass of an image given its height or width.  In fact these macros may
     * return non-zero even though the sub-image is empty, because the other
     * dimension may be empty for a small image.
     */
    #define PNG_PASS_ROWS(height, pass) (((height)+(((1<<PNG_PASS_ROW_SHIFT(pass))\
       -1)-PNG_PASS_START_ROW(pass)))>>PNG_PASS_ROW_SHIFT(pass))
    #define PNG_PASS_COLS(width, pass) (((width)+(((1<<PNG_PASS_COL_SHIFT(pass))\
       -1)-PNG_PASS_START_COL(pass)))>>PNG_PASS_COL_SHIFT(pass))

    /* For the reader row callbacks (both progressive and sequential) it is
     * necessary to find the row in the output image given a row in an interlaced
     * image, so two more macros:
     */
    #define PNG_ROW_FROM_PASS_ROW(y_in, pass) \
       (((y_in)<<PNG_PASS_ROW_SHIFT(pass))+PNG_PASS_START_ROW(pass))
    #define PNG_COL_FROM_PASS_COL(x_in, pass) \
       (((x_in)<<PNG_PASS_COL_SHIFT(pass))+PNG_PASS_START_COL(pass))

    /* Two macros which return a boolean (0 or 1) saying whether the given row
     * or column is in a particular pass.  These use a common utility macro that
     * returns a mask for a given pass - the offset 'off' selects the row or
     * column version.  The mask has the appropriate bit set for each column in
     * the tile.
     */
    #define PNG_PASS_MASK(pass,off) ( \
       ((0x110145AF>>(((7-(off))-(pass))<<2)) & 0xF) | \
       ((0x01145AF0>>(((7-(off))-(pass))<<2)) & 0xF0))

    #define PNG_ROW_IN_INTERLACE_PASS(y, pass) \
       ((PNG_PASS_MASK(pass,0) >> ((y)&7)) & 1)
    #define PNG_COL_IN_INTERLACE_PASS(x, pass) \
       ((PNG_PASS_MASK(pass,1) >> ((x)&7)) & 1)

    #ifdef PNG_READ_COMPOSITE_NODIV_SUPPORTED
    /* With these routines we avoid an integer divide, which will be slower on
     * most machines.  However, it does take more operations than the corresponding
     * divide method, so it may be slower on a few RISC systems.  There are two
     * shifts (by 8 or 16 bits) and an addition, versus a single integer divide.
     *
     * Note that the rounding factors are NOT supposed to be the same!  128 and
     * 32768 are correct for the NODIV code; 127 and 32767 are correct for the
     * standard method.
     *
     * [Optimized code by Greg Roelofs and Mark Adler...blame us for bugs. :-) ]
     */

     /* fg and bg should be in `gamma 1.0' space; alpha is the opacity */

    #  define png_composite(composite, fg, alpha, bg)         \
         { png_uint_16 temp = (png_uint_16)((png_uint_16)(fg) \
               * (png_uint_16)(alpha)                         \
               + (png_uint_16)(bg)*(png_uint_16)(255          \
               - (png_uint_16)(alpha)) + 128);                \
           (composite) = (png_byte)((temp + (temp >> 8)) >> 8); }

    #  define png_composite_16(composite, fg, alpha, bg)       \
         { png_uint_32 temp = (png_uint_32)((png_uint_32)(fg)  \
               * (png_uint_32)(alpha)                          \
               + (png_uint_32)(bg)*(65535                      \
               - (png_uint_32)(alpha)) + 32768);               \
           (composite) = (png_uint_16)((temp + (temp >> 16)) >> 16); }

    #else  /* Standard method using integer division */

    #  define png_composite(composite, fg, alpha, bg)                          \
         (composite) = (png_byte)(((png_uint_16)(fg) * (png_uint_16)(alpha) +  \
         (png_uint_16)(bg) * (png_uint_16)(255 - (png_uint_16)(alpha)) +       \
         127) / 255)

    #  define png_composite_16(composite, fg, alpha, bg)                         \
         (composite) = (png_uint_16)(((png_uint_32)(fg) * (png_uint_32)(alpha) + \
         (png_uint_32)(bg)*(png_uint_32)(65535 - (png_uint_32)(alpha)) +         \
         32767) / 65535)
    #endif /* PNG_READ_COMPOSITE_NODIV_SUPPORTED */

    #ifdef PNG_READ_INT_FUNCTIONS_SUPPORTED
    PNG_EXPORT(201, png_uint_32, png_get_uint_32, (png_const_bytep buf));
    PNG_EXPORT(202, png_uint_16, png_get_uint_16, (png_const_bytep buf));
    PNG_EXPORT(203, png_int_32, png_get_int_32, (png_const_bytep buf));
    #endif

    PNG_EXPORT(204, png_uint_32, png_get_uint_31, (png_const_structrp png_ptr,
        png_const_bytep buf));
    /* No png_get_int_16 -- may be added if there's a real need for it. */

    /* Place a 32-bit number into a buffer in PNG byte order (big-endian). */
    #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
    PNG_EXPORT(205, void, png_save_uint_32, (png_bytep buf, png_uint_32 i));
    #endif
    #ifdef PNG_SAVE_INT_32_SUPPORTED
    PNG_EXPORT(206, void, png_save_int_32, (png_bytep buf, png_int_32 i));
    #endif

    /* Place a 16-bit number into a buffer in PNG byte order.
     * The parameter is declared unsigned int, not png_uint_16,
     * just to avoid potential problems on pre-ANSI C compilers.
     */
    #ifdef PNG_WRITE_INT_FUNCTIONS_SUPPORTED
    PNG_EXPORT(207, void, png_save_uint_16, (png_bytep buf, unsigned int i));
    /* No png_save_int_16 -- may be added if there's a real need for it. */
    #endif

    #ifdef PNG_USE_READ_MACROS
    /* Inline macros to do direct reads of bytes from the input buffer.
     * The png_get_int_32() routine assumes we are using two's complement
     * format for negative values, which is almost certainly true.
     */
    #  define PNG_get_uint_32(buf) \
         (((png_uint_32)(*(buf)) << 24) + \
          ((png_uint_32)(*((buf) + 1)) << 16) + \
          ((png_uint_32)(*((buf) + 2)) << 8) + \
          ((png_uint_32)(*((buf) + 3))))

       /* From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the
        * function) incorrectly returned a value of type png_uint_32.
        */
    #  define PNG_get_uint_16(buf) \
         ((png_uint_16) \
          (((unsigned int)(*(buf)) << 8) + \
           ((unsigned int)(*((buf) + 1)))))

    #  define PNG_get_int_32(buf) \
         ((png_int_32)((*(buf) & 0x80) \
          ? -((png_int_32)((png_get_uint_32(buf) ^ 0xffffffffL) + 1)) \
          : (png_int_32)png_get_uint_32(buf)))

       /* If PNG_PREFIX is defined the same thing as below happens in pnglibconf.h,
        * but defining a macro name prefixed with PNG_PREFIX.
        */
    #  ifndef PNG_PREFIX
    #     define png_get_uint_32(buf) PNG_get_uint_32(buf)
    #     define png_get_uint_16(buf) PNG_get_uint_16(buf)
    #     define png_get_int_32(buf)  PNG_get_int_32(buf)
    #  endif
    #else
    #  ifdef PNG_PREFIX
          /* No macros; revert to the (redefined) function */
    #     define PNG_get_uint_32 (png_get_uint_32)
    #     define PNG_get_uint_16 (png_get_uint_16)
    #     define PNG_get_int_32  (png_get_int_32)
    #  endif
    #endif

    /*******************************************************************************
     *  SIMPLIFIED API
     *******************************************************************************
     *
     * Please read the documentation in libpng-manual.txt (TODO: write said
     * documentation) if you don't understand what follows.
     *
     * The simplified API hides the details of both libpng and the PNG file format
     * itself.  It allows PNG files to be read into a very limited number of
     * in-memory bitmap formats or to be written from the same formats.  If these
     * formats do not accomodate your needs then you can, and should, use the more
     * sophisticated APIs above - these support a wide variety of in-memory formats
     * and a wide variety of sophisticated transformations to those formats as well
     * as a wide variety of APIs to manipulate ancillary information.
     *
     * To read a PNG file using the simplified API:
     *
     * 1) Declare a 'png_image' structure (see below) on the stack and set the
     *    version field to PNG_IMAGE_VERSION.
     * 2) Call the appropriate png_image_begin_read... function.
     * 3) Set the png_image 'format' member to the required sample format.
     * 4) Allocate a buffer for the image and, if required, the color-map.
     * 5) Call png_image_finish_read to read the image and, if required, the
     *    color-map into your buffers.
     *
     * There are no restrictions on the format of the PNG input itself; all valid
     * color types, bit depths, and interlace methods are acceptable, and the
     * input image is transformed as necessary to the requested in-memory format
     * during the png_image_finish_read() step.  The only caveat is that if you
     * request a color-mapped image from a PNG that is full-color or makes
     * complex use of an alpha channel the transformation is extremely lossy and the
     * result may look terrible.
     *
     * To write a PNG file using the simplified API:
     *
     * 1) Declare a 'png_image' structure on the stack and memset() it to all zero.
     * 2) Initialize the members of the structure that describe the image, setting
     *    the 'format' member to the format of the image samples.
     * 3) Call the appropriate png_image_write... function with a pointer to the
     *    image and, if necessary, the color-map to write the PNG data.
     *
     * png_image is a structure that describes the in-memory format of an image
     * when it is being read or defines the in-memory format of an image that you
     * need to write:
     */
    #define PNG_IMAGE_VERSION 1

    typedef struct png_control *png_controlp;
    typedef struct
    {
       png_controlp opaque;    /* Initialize to NULL, free with png_image_free */
       png_uint_32  version;   /* Set to PNG_IMAGE_VERSION */
       png_uint_32  width;     /* Image width in pixels (columns) */
       png_uint_32  height;    /* Image height in pixels (rows) */
       png_uint_32  format;    /* Image format as defined below */
       png_uint_32  flags;     /* A bit mask containing informational flags */
       png_uint_32  colormap_entries;
                               /* Number of entries in the color-map */

       /* In the event of an error or warning the following field will be set to a
        * non-zero value and the 'message' field will contain a '\0' terminated
        * string with the libpng error or warning message.  If both warnings and
        * an error were encountered, only the error is recorded.  If there
        * are multiple warnings, only the first one is recorded.
        *
        * The upper 30 bits of this value are reserved, the low two bits contain
        * a value as follows:
        */
    #  define PNG_IMAGE_WARNING 1
    #  define PNG_IMAGE_ERROR 2
       /*
        * The result is a two bit code such that a value more than 1 indicates
        * a failure in the API just called:
        *
        *    0 - no warning or error
        *    1 - warning
        *    2 - error
        *    3 - error preceded by warning
        */
    #  define PNG_IMAGE_FAILED(png_cntrl) ((((png_cntrl).warning_or_error)&0x03)>1)

       png_uint_32  warning_or_error;

       char         message[64];
    } png_image, *png_imagep;

    /* The samples of the image have one to four channels whose components have
     * original values in the range 0 to 1.0:
     *
     * 1: A single gray or luminance channel (G).
     * 2: A gray/luminance channel and an alpha channel (GA).
     * 3: Three red, green, blue color channels (RGB).
     * 4: Three color channels and an alpha channel (RGBA).
     *
     * The components are encoded in one of two ways:
     *
     * a) As a small integer, value 0..255, contained in a single byte.  For the
     * alpha channel the original value is simply value/255.  For the color or
     * luminance channels the value is encoded according to the sRGB specification
     * and matches the 8-bit format expected by typical display devices.
     *
     * The color/gray channels are not scaled (pre-multiplied) by the alpha
     * channel and are suitable for passing to color management software.
     *
     * b) As a value in the range 0..65535, contained in a 2-byte integer.  All
     * channels can be converted to the original value by dividing by 65535; all
     * channels are linear.  Color channels use the RGB encoding (RGB end-points) of
     * the sRGB specification.  This encoding is identified by the
     * PNG_FORMAT_FLAG_LINEAR flag below.
     *
     * When the simplified API needs to convert between sRGB and linear colorspaces,
     * the actual sRGB transfer curve defined in the sRGB specification (see the
     * article at http://en.wikipedia.org/wiki/SRGB) is used, not the gamma=1/2.2
     * approximation used elsewhere in libpng.
     *
     * When an alpha channel is present it is expected to denote pixel coverage
     * of the color or luminance channels and is returned as an associated alpha
     * channel: the color/gray channels are scaled (pre-multiplied) by the alpha
     * value.
     *
     * The samples are either contained directly in the image data, between 1 and 8
     * bytes per pixel according to the encoding, or are held in a color-map indexed
     * by bytes in the image data.  In the case of a color-map the color-map entries
     * are individual samples, encoded as above, and the image data has one byte per
     * pixel to select the relevant sample from the color-map.
     */

    /* PNG_FORMAT_*
     *
     * #defines to be used in png_image::format.  Each #define identifies a
     * particular layout of sample data and, if present, alpha values.  There are
     * separate defines for each of the two component encodings.
     *
     * A format is built up using single bit flag values.  All combinations are
     * valid.  Formats can be built up from the flag values or you can use one of
     * the predefined values below.  When testing formats always use the FORMAT_FLAG
     * macros to test for individual features - future versions of the library may
     * add new flags.
     *
     * When reading or writing color-mapped images the format should be set to the
     * format of the entries in the color-map then png_image_{read,write}_colormap
     * called to read or write the color-map and set the format correctly for the
     * image data.  Do not set the PNG_FORMAT_FLAG_COLORMAP bit directly!
     *
     * NOTE: libpng can be built with particular features disabled, if you see
     * compiler errors because the definition of one of the following flags has been
     * compiled out it is because libpng does not have the required support.  It is
     * possible, however, for the libpng configuration to enable the format on just
     * read or just write; in that case you may see an error at run time.  You can
     * guard against this by checking for the definition of the appropriate
     * "_SUPPORTED" macro, one of:
     *
     *    PNG_SIMPLIFIED_{READ,WRITE}_{BGR,AFIRST}_SUPPORTED
     */
    #define PNG_FORMAT_FLAG_ALPHA    0x01U /* format with an alpha channel */
    #define PNG_FORMAT_FLAG_COLOR    0x02U /* color format: otherwise grayscale */
    #define PNG_FORMAT_FLAG_LINEAR   0x04U /* 2 byte channels else 1 byte */
    #define PNG_FORMAT_FLAG_COLORMAP 0x08U /* image data is color-mapped */

    #ifdef PNG_FORMAT_BGR_SUPPORTED
    #  define PNG_FORMAT_FLAG_BGR    0x10U /* BGR colors, else order is RGB */
    #endif

    #ifdef PNG_FORMAT_AFIRST_SUPPORTED
    #  define PNG_FORMAT_FLAG_AFIRST 0x20U /* alpha channel comes first */
    #endif

    /* Commonly used formats have predefined macros.
     *
     * First the single byte (sRGB) formats:
     */
    #define PNG_FORMAT_GRAY 0
    #define PNG_FORMAT_GA   PNG_FORMAT_FLAG_ALPHA
    #define PNG_FORMAT_AG   (PNG_FORMAT_GA|PNG_FORMAT_FLAG_AFIRST)
    #define PNG_FORMAT_RGB  PNG_FORMAT_FLAG_COLOR
    #define PNG_FORMAT_BGR  (PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_BGR)
    #define PNG_FORMAT_RGBA (PNG_FORMAT_RGB|PNG_FORMAT_FLAG_ALPHA)
    #define PNG_FORMAT_ARGB (PNG_FORMAT_RGBA|PNG_FORMAT_FLAG_AFIRST)
    #define PNG_FORMAT_BGRA (PNG_FORMAT_BGR|PNG_FORMAT_FLAG_ALPHA)
    #define PNG_FORMAT_ABGR (PNG_FORMAT_BGRA|PNG_FORMAT_FLAG_AFIRST)

    /* Then the linear 2-byte formats.  When naming these "Y" is used to
     * indicate a luminance (gray) channel.
     */
    #define PNG_FORMAT_LINEAR_Y PNG_FORMAT_FLAG_LINEAR
    #define PNG_FORMAT_LINEAR_Y_ALPHA (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_ALPHA)
    #define PNG_FORMAT_LINEAR_RGB (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR)
    #define PNG_FORMAT_LINEAR_RGB_ALPHA \
       (PNG_FORMAT_FLAG_LINEAR|PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_ALPHA)

    /* With color-mapped formats the image data is one byte for each pixel, the byte
     * is an index into the color-map which is formatted as above.  To obtain a
     * color-mapped format it is sufficient just to add the PNG_FOMAT_FLAG_COLORMAP
     * to one of the above definitions, or you can use one of the definitions below.
     */
    #define PNG_FORMAT_RGB_COLORMAP  (PNG_FORMAT_RGB|PNG_FORMAT_FLAG_COLORMAP)
    #define PNG_FORMAT_BGR_COLORMAP  (PNG_FORMAT_BGR|PNG_FORMAT_FLAG_COLORMAP)
    #define PNG_FORMAT_RGBA_COLORMAP (PNG_FORMAT_RGBA|PNG_FORMAT_FLAG_COLORMAP)
    #define PNG_FORMAT_ARGB_COLORMAP (PNG_FORMAT_ARGB|PNG_FORMAT_FLAG_COLORMAP)
    #define PNG_FORMAT_BGRA_COLORMAP (PNG_FORMAT_BGRA|PNG_FORMAT_FLAG_COLORMAP)
    #define PNG_FORMAT_ABGR_COLORMAP (PNG_FORMAT_ABGR|PNG_FORMAT_FLAG_COLORMAP)

    /* PNG_IMAGE macros
     *
     * These are convenience macros to derive information from a png_image
     * structure.  The PNG_IMAGE_SAMPLE_ macros return values appropriate to the
     * actual image sample values - either the entries in the color-map or the
     * pixels in the image.  The PNG_IMAGE_PIXEL_ macros return corresponding values
     * for the pixels and will always return 1 for color-mapped formats.  The
     * remaining macros return information about the rows in the image and the
     * complete image.
     *
     * NOTE: All the macros that take a png_image::format parameter are compile time
     * constants if the format parameter is, itself, a constant.  Therefore these
     * macros can be used in array declarations and case labels where required.
     * Similarly the macros are also pre-processor constants (sizeof is not used) so
     * they can be used in #if tests.
     *
     * First the information about the samples.
     */
    #define PNG_IMAGE_SAMPLE_CHANNELS(fmt)\
       (((fmt)&(PNG_FORMAT_FLAG_COLOR|PNG_FORMAT_FLAG_ALPHA))+1)
       /* Return the total number of channels in a given format: 1..4 */

    #define PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt)\
       ((((fmt) & PNG_FORMAT_FLAG_LINEAR) >> 2)+1)
       /* Return the size in bytes of a single component of a pixel or color-map
        * entry (as appropriate) in the image: 1 or 2.
        */

    #define PNG_IMAGE_SAMPLE_SIZE(fmt)\
       (PNG_IMAGE_SAMPLE_CHANNELS(fmt) * PNG_IMAGE_SAMPLE_COMPONENT_SIZE(fmt))
       /* This is the size of the sample data for one sample.  If the image is
        * color-mapped it is the size of one color-map entry (and image pixels are
        * one byte in size), otherwise it is the size of one image pixel.
        */

    #define PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(fmt)\
       (PNG_IMAGE_SAMPLE_CHANNELS(fmt) * 256)
       /* The maximum size of the color-map required by the format expressed in a
        * count of components.  This can be used to compile-time allocate a
        * color-map:
        *
        * png_uint_16 colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(linear_fmt)];
        *
        * png_byte colormap[PNG_IMAGE_MAXIMUM_COLORMAP_COMPONENTS(sRGB_fmt)];
        *
        * Alternatively use the PNG_IMAGE_COLORMAP_SIZE macro below to use the
        * information from one of the png_image_begin_read_ APIs and dynamically
        * allocate the required memory.
        */

    /* Corresponding information about the pixels */
    #define PNG_IMAGE_PIXEL_(test,fmt)\
       (((fmt)&PNG_FORMAT_FLAG_COLORMAP)?1:test(fmt))

    #define PNG_IMAGE_PIXEL_CHANNELS(fmt)\
       PNG_IMAGE_PIXEL_(PNG_IMAGE_SAMPLE_CHANNELS,fmt)
       /* The number of separate channels (components) in a pixel; 1 for a
        * color-mapped image.
        */

    #define PNG_IMAGE_PIXEL_COMPONENT_SIZE(fmt)\
       PNG_IMAGE_PIXEL_(PNG_IMAGE_SAMPLE_COMPONENT_SIZE,fmt)
       /* The size, in bytes, of each component in a pixel; 1 for a color-mapped
        * image.
        */

    #define PNG_IMAGE_PIXEL_SIZE(fmt) PNG_IMAGE_PIXEL_(PNG_IMAGE_SAMPLE_SIZE,fmt)
       /* The size, in bytes, of a complete pixel; 1 for a color-mapped image. */

    /* Information about the whole row, or whole image */
    #define PNG_IMAGE_ROW_STRIDE(image)\
       (PNG_IMAGE_PIXEL_CHANNELS((image).format) * (image).width)
       /* Return the total number of components in a single row of the image; this
        * is the minimum 'row stride', the minimum count of components between each
        * row.  For a color-mapped image this is the minimum number of bytes in a
        * row.
        */

    #define PNG_IMAGE_BUFFER_SIZE(image, row_stride)\
       (PNG_IMAGE_PIXEL_COMPONENT_SIZE((image).format)*(image).height*(row_stride))
       /* Return the size, in bytes, of an image buffer given a png_image and a row
        * stride - the number of components to leave space for in each row.
        */

    #define PNG_IMAGE_SIZE(image)\
       PNG_IMAGE_BUFFER_SIZE(image, PNG_IMAGE_ROW_STRIDE(image))
       /* Return the size, in bytes, of the image in memory given just a png_image;
        * the row stride is the minimum stride required for the image.
        */

    #define PNG_IMAGE_COLORMAP_SIZE(image)\
       (PNG_IMAGE_SAMPLE_SIZE((image).format) * (image).colormap_entries)
       /* Return the size, in bytes, of the color-map of this image.  If the image
        * format is not a color-map format this will return a size sufficient for
        * 256 entries in the given format; check PNG_FORMAT_FLAG_COLORMAP if
        * you don't want to allocate a color-map in this case.
        */

    /* PNG_IMAGE_FLAG_*
     *
     * Flags containing additional information about the image are held in the
     * 'flags' field of png_image.
     */
    #define PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB 0x01
       /* This indicates the the RGB values of the in-memory bitmap do not
        * correspond to the red, green and blue end-points defined by sRGB.
        */

    #define PNG_IMAGE_FLAG_FAST 0x02
       /* On write emphasise speed over compression; the resultant PNG file will be
        * larger but will be produced significantly faster, particular for large
        * images.  Do not use this option for images which will be distributed, only
        * used it when producing intermediate files that will be read back in
        * repeatedly.  For a typical 24-bit image the option will double the read
        * speed at the cost of increasing the image size by 25%, however for many
        * more compressible images the PNG file can be 10 times larger with only a
        * slight speed gain.
        */

    #define PNG_IMAGE_FLAG_16BIT_sRGB 0x04
       /* On read if the image is a 16-bit per component image and there is no gAMA
        * or sRGB chunk assume that the components are sRGB encoded.  Notice that
        * images output by the simplified API always have gamma information; setting
        * this flag only affects the interpretation of 16-bit images from an
        * external source.  It is recommended that the application expose this flag
        * to the user; the user can normally easily recognize the difference between
        * linear and sRGB encoding.  This flag has no effect on write - the data
        * passed to the write APIs must have the correct encoding (as defined
        * above.)
        *
        * If the flag is not set (the default) input 16-bit per component data is
        * assumed to be linear.
        *
        * NOTE: the flag can only be set after the png_image_begin_read_ call,
        * because that call initializes the 'flags' field.
        */

    #ifdef PNG_SIMPLIFIED_READ_SUPPORTED
    /* READ APIs
     * ---------
     *
     * The png_image passed to the read APIs must have been initialized by setting
     * the png_controlp field 'opaque' to NULL (or, safer, memset the whole thing.)
     */
    #ifdef PNG_STDIO_SUPPORTED
    PNG_EXPORT(234, int, png_image_begin_read_from_file, (png_imagep image,
       const char *file_name));
       /* The named file is opened for read and the image header is filled in
        * from the PNG header in the file.
        */

    PNG_EXPORT(235, int, png_image_begin_read_from_stdio, (png_imagep image,
       FILE* file));
       /* The PNG header is read from the stdio FILE object. */
    #endif /* PNG_STDIO_SUPPORTED */

    PNG_EXPORT(236, int, png_image_begin_read_from_memory, (png_imagep image,
       png_const_voidp memory, png_size_t size));
       /* The PNG header is read from the given memory buffer. */

    PNG_EXPORT(237, int, png_image_finish_read, (png_imagep image,
       png_const_colorp background, void *buffer, png_int_32 row_stride,
       void *colormap));
       /* Finish reading the image into the supplied buffer and clean up the
        * png_image structure.
        *
        * row_stride is the step, in byte or 2-byte units as appropriate,
        * between adjacent rows.  A positive stride indicates that the top-most row
        * is first in the buffer - the normal top-down arrangement.  A negative
        * stride indicates that the bottom-most row is first in the buffer.
        *
        * background need only be supplied if an alpha channel must be removed from
        * a png_byte format and the removal is to be done by compositing on a solid
        * color; otherwise it may be NULL and any composition will be done directly
        * onto the buffer.  The value is an sRGB color to use for the background,
        * for grayscale output the green channel is used.
        *
        * background must be supplied when an alpha channel must be removed from a
        * single byte color-mapped output format, in other words if:
        *
        * 1) The original format from png_image_begin_read_from_* had
        *    PNG_FORMAT_FLAG_ALPHA set.
        * 2) The format set by the application does not.
        * 3) The format set by the application has PNG_FORMAT_FLAG_COLORMAP set and
        *    PNG_FORMAT_FLAG_LINEAR *not* set.
        *
        * For linear output removing the alpha channel is always done by compositing
        * on black and background is ignored.
        *
        * colormap must be supplied when PNG_FORMAT_FLAG_COLORMAP is set.  It must
        * be at least the size (in bytes) returned by PNG_IMAGE_COLORMAP_SIZE.
        * image->colormap_entries will be updated to the actual number of entries
        * written to the colormap; this may be less than the original value.
        */

    PNG_EXPORT(238, void, png_image_free, (png_imagep image));
       /* Free any data allocated by libpng in image->opaque, setting the pointer to
        * NULL.  May be called at any time after the structure is initialized.
        */
    #endif /* PNG_SIMPLIFIED_READ_SUPPORTED */

    #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
    #ifdef PNG_STDIO_SUPPORTED
    /* WRITE APIS
     * ----------
     * For write you must initialize a png_image structure to describe the image to
     * be written.  To do this use memset to set the whole structure to 0 then
     * initialize fields describing your image.
     *
     * version: must be set to PNG_IMAGE_VERSION
     * opaque: must be initialized to NULL
     * width: image width in pixels
     * height: image height in rows
     * format: the format of the data (image and color-map) you wish to write
     * flags: set to 0 unless one of the defined flags applies; set
     *    PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB for color format images where the RGB
     *    values do not correspond to the colors in sRGB.
     * colormap_entries: set to the number of entries in the color-map (0 to 256)
     */
    PNG_EXPORT(239, int, png_image_write_to_file, (png_imagep image,
       const char *file, int convert_to_8bit, const void *buffer,
       png_int_32 row_stride, const void *colormap));
       /* Write the image to the named file. */

    PNG_EXPORT(240, int, png_image_write_to_stdio, (png_imagep image, FILE *file,
       int convert_to_8_bit, const void *buffer, png_int_32 row_stride,
       const void *colormap));
       /* Write the image to the given (FILE*). */

    /* With both write APIs if image is in one of the linear formats with 16-bit
     * data then setting convert_to_8_bit will cause the output to be an 8-bit PNG
     * gamma encoded according to the sRGB specification, otherwise a 16-bit linear
     * encoded PNG file is written.
     *
     * With color-mapped data formats the colormap parameter point to a color-map
     * with at least image->colormap_entries encoded in the specified format.  If
     * the format is linear the written PNG color-map will be converted to sRGB
     * regardless of the convert_to_8_bit flag.
     *
     * With all APIs row_stride is handled as in the read APIs - it is the spacing
     * from one row to the next in component sized units (1 or 2 bytes) and if
     * negative indicates a bottom-up row layout in the buffer.
     *
     * Note that the write API does not support interlacing or sub-8-bit pixels.
     */
    #endif /* PNG_STDIO_SUPPORTED */
    #endif /* PNG_SIMPLIFIED_WRITE_SUPPORTED */
    /*******************************************************************************
     *  END OF SIMPLIFIED API
     ******************************************************************************/

    #ifdef PNG_CHECK_FOR_INVALID_INDEX_SUPPORTED
    PNG_EXPORT(242, void, png_set_check_for_invalid_index,
        (png_structrp png_ptr, int allowed));
    #  ifdef PNG_GET_PALETTE_MAX_SUPPORTED
    PNG_EXPORT(243, int, png_get_palette_max, (png_const_structp png_ptr,
        png_const_infop info_ptr));
    #  endif
    #endif /* CHECK_FOR_INVALID_INDEX */

    /*******************************************************************************
     *  IMPLEMENTATION OPTIONS
     *******************************************************************************
     *
     * Support for arbitrary implementation-specific optimizations.  The API allows
     * particular options to be turned on or off.  'Option' is the number of the
     * option and 'onoff' is 0 (off) or non-0 (on).  The value returned is given
     * by the PNG_OPTION_ defines below.
     *
     * HARDWARE: normally hardware capabilites, such as the Intel SSE instructions,
     *           are detected at run time, however sometimes it may be impossible
     *           to do this in user mode, in which case it is necessary to discover
     *           the capabilities in an OS specific way.  Such capabilities are
     *           listed here when libpng has support for them and must be turned
     *           ON by the application if present.
     *
     * SOFTWARE: sometimes software optimizations actually result in performance
     *           decrease on some architectures or systems, or with some sets of
     *           PNG images.  'Software' options allow such optimizations to be
     *           selected at run time.
     */
    #ifdef PNG_SET_OPTION_SUPPORTED
    #ifdef PNG_ARM_NEON_API_SUPPORTED
    #  define PNG_ARM_NEON   0 /* HARDWARE: ARM Neon SIMD instructions supported */
    #endif
    #define PNG_MAXIMUM_INFLATE_WINDOW 2 /* SOFTWARE: force maximum window */
    #define PNG_OPTION_NEXT  4 /* Next option - numbers must be even */

    /* Return values: NOTE: there are four values and 'off' is *not* zero */
    #define PNG_OPTION_UNSET   0 /* Unset - defaults to off */
    #define PNG_OPTION_INVALID 1 /* Option number out of range */
    #define PNG_OPTION_OFF     2
    #define PNG_OPTION_ON      3

    PNG_EXPORT(244, int, png_set_option, (png_structrp png_ptr, int option,
       int onoff));
    #endif

    /*******************************************************************************
     *  END OF HARDWARE OPTIONS
     ******************************************************************************/

    /* Maintainer: Put new public prototypes here ^, in libpng.3, and project
     * defs, scripts/pnglibconf.h, and scripts/pnglibconf.h.prebuilt
     */

    /* The last ordinal number (this is the *last* one already used; the next
     * one to use is one more than this.)  Maintainer, remember to add an entry to
     * scripts/symbols.def as well.
     */
    #ifdef PNG_EXPORT_LAST_ORDINAL
      PNG_EXPORT_LAST_ORDINAL(244);
    #endif

    #ifdef __cplusplus
    }
    #endif

    #endif /* PNG_VERSION_INFO_ONLY */
    /* Do not put anything past this line */
    #endif /* PNG_H */