    /* pnginfo.h - header file for PNG reference library
     *
     * 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.)
     *
     * Last changed in libpng 1.6.1 [March 28, 2013]
     *
     * This code is released under the libpng license.
     * For conditions of distribution and use, see the disclaimer
     * and license in png.h
     */

     /* png_info is a structure that holds the information in a PNG file so
     * that the application can find out the characteristics of the image.
     * If you are reading the file, this structure will tell you what is
     * in the PNG file.  If you are writing the file, fill in the information
     * you want to put into the PNG file, using png_set_*() functions, then
     * call png_write_info().
     *
     * The names chosen should be very close to the PNG specification, so
     * consult that document for information about the meaning of each field.
     *
     * With libpng < 0.95, it was only possible to directly set and read the
     * the values in the png_info_struct, which meant that the contents and
     * order of the values had to remain fixed.  With libpng 0.95 and later,
     * however, there are now functions that abstract the contents of
     * png_info_struct from the application, so this makes it easier to use
     * libpng with dynamic libraries, and even makes it possible to use
     * libraries that don't have all of the libpng ancillary chunk-handing
     * functionality.  In libpng-1.5.0 this was moved into a separate private
     * file that is not visible to applications.
     *
     * The following members may have allocated storage attached that should be
     * cleaned up before the structure is discarded: palette, trans, text,
     * pcal_purpose, pcal_units, pcal_params, hist, iccp_name, iccp_profile,
     * splt_palettes, scal_unit, row_pointers, and unknowns.   By default, these
     * are automatically freed when the info structure is deallocated, if they were
     * allocated internally by libpng.  This behavior can be changed by means
     * of the png_data_freer() function.
     *
     * More allocation details: all the chunk-reading functions that
     * change these members go through the corresponding png_set_*
     * functions.  A function to clear these members is available: see
     * png_free_data().  The png_set_* functions do not depend on being
     * able to point info structure members to any of the storage they are
     * passed (they make their own copies), EXCEPT that the png_set_text
     * functions use the same storage passed to them in the text_ptr or
     * itxt_ptr structure argument, and the png_set_rows and png_set_unknowns
     * functions do not make their own copies.
     */
    #ifndef PNGINFO_H
    #define PNGINFO_H

    struct png_info_def
    {
       /* The following are necessary for every PNG file */
       png_uint_32 width;  /* width of image in pixels (from IHDR) */
       png_uint_32 height; /* height of image in pixels (from IHDR) */
       png_uint_32 valid;  /* valid chunk data (see PNG_INFO_ below) */
       png_size_t rowbytes; /* bytes needed to hold an untransformed row */
       png_colorp palette;      /* array of color values (valid & PNG_INFO_PLTE) */
       png_uint_16 num_palette; /* number of color entries in "palette" (PLTE) */
       png_uint_16 num_trans;   /* number of transparent palette color (tRNS) */
       png_byte bit_depth;      /* 1, 2, 4, 8, or 16 bits/channel (from IHDR) */
       png_byte color_type;     /* see PNG_COLOR_TYPE_ below (from IHDR) */
       /* The following three should have been named *_method not *_type */
       png_byte compression_type; /* must be PNG_COMPRESSION_TYPE_BASE (IHDR) */
       png_byte filter_type;    /* must be PNG_FILTER_TYPE_BASE (from IHDR) */
       png_byte interlace_type; /* One of PNG_INTERLACE_NONE, PNG_INTERLACE_ADAM7 */

       /* The following are set by png_set_IHDR, called from the application on
        * write, but the are never actually used by the write code.
        */
       png_byte channels;       /* number of data channels per pixel (1, 2, 3, 4) */
       png_byte pixel_depth;    /* number of bits per pixel */
       png_byte spare_byte;     /* to align the data, and for future use */

    #ifdef PNG_READ_SUPPORTED
       /* This is never set during write */
       png_byte signature[8];   /* magic bytes read by libpng from start of file */
    #endif

       /* The rest of the data is optional.  If you are reading, check the
        * valid field to see if the information in these are valid.  If you
        * are writing, set the valid field to those chunks you want written,
        * and initialize the appropriate fields below.
        */

    #if defined(PNG_COLORSPACE_SUPPORTED) || defined(PNG_GAMMA_SUPPORTED)
       /* png_colorspace only contains 'flags' if neither GAMMA or COLORSPACE are
        * defined.  When COLORSPACE is switched on all the colorspace-defining
        * chunks should be enabled, when GAMMA is switched on all the gamma-defining
        * chunks should be enabled.  If this is not done it becomes possible to read
        * inconsistent PNG files and assign a probably incorrect interpretation to
        * the information.  (In other words, by carefully choosing which chunks to
        * recognize the system configuration can select an interpretation for PNG
        * files containing ambiguous data and this will result in inconsistent
        * behavior between different libpng builds!)
        */
       png_colorspace colorspace;
    #endif

    #ifdef PNG_iCCP_SUPPORTED
       /* iCCP chunk data. */
       png_charp iccp_name;     /* profile name */
       png_bytep iccp_profile;  /* International Color Consortium profile data */
       png_uint_32 iccp_proflen;  /* ICC profile data length */
    #endif

    #ifdef PNG_TEXT_SUPPORTED
       /* The tEXt, and zTXt chunks contain human-readable textual data in
        * uncompressed, compressed, and optionally compressed forms, respectively.
        * The data in "text" is an array of pointers to uncompressed,
        * null-terminated C strings. Each chunk has a keyword that describes the
        * textual data contained in that chunk.  Keywords are not required to be
        * unique, and the text string may be empty.  Any number of text chunks may
        * be in an image.
        */
       int num_text; /* number of comments read or comments to write */
       int max_text; /* current size of text array */
       png_textp text; /* array of comments read or comments to write */
    #endif /* PNG_TEXT_SUPPORTED */

    #ifdef PNG_tIME_SUPPORTED
       /* The tIME chunk holds the last time the displayed image data was
        * modified.  See the png_time struct for the contents of this struct.
        */
       png_time mod_time;
    #endif

    #ifdef PNG_sBIT_SUPPORTED
       /* The sBIT chunk specifies the number of significant high-order bits
        * in the pixel data.  Values are in the range [1, bit_depth], and are
        * only specified for the channels in the pixel data.  The contents of
        * the low-order bits is not specified.  Data is valid if
        * (valid & PNG_INFO_sBIT) is non-zero.
        */
       png_color_8 sig_bit; /* significant bits in color channels */
    #endif

    #if defined(PNG_tRNS_SUPPORTED) || defined(PNG_READ_EXPAND_SUPPORTED) || \
    defined(PNG_READ_BACKGROUND_SUPPORTED)
       /* The tRNS chunk supplies transparency data for paletted images and
        * other image types that don't need a full alpha channel.  There are
        * "num_trans" transparency values for a paletted image, stored in the
        * same order as the palette colors, starting from index 0.  Values
        * for the data are in the range [0, 255], ranging from fully transparent
        * to fully opaque, respectively.  For non-paletted images, there is a
        * single color specified that should be treated as fully transparent.
        * Data is valid if (valid & PNG_INFO_tRNS) is non-zero.
        */
       png_bytep trans_alpha;    /* alpha values for paletted image */
       png_color_16 trans_color; /* transparent color for non-palette image */
    #endif

    #if defined(PNG_bKGD_SUPPORTED) || defined(PNG_READ_BACKGROUND_SUPPORTED)
       /* The bKGD chunk gives the suggested image background color if the
        * display program does not have its own background color and the image
        * is needs to composited onto a background before display.  The colors
        * in "background" are normally in the same color space/depth as the
        * pixel data.  Data is valid if (valid & PNG_INFO_bKGD) is non-zero.
        */
       png_color_16 background;
    #endif

    #ifdef PNG_oFFs_SUPPORTED
       /* The oFFs chunk gives the offset in "offset_unit_type" units rightwards
        * and downwards from the top-left corner of the display, page, or other
        * application-specific co-ordinate space.  See the PNG_OFFSET_ defines
        * below for the unit types.  Valid if (valid & PNG_INFO_oFFs) non-zero.
        */
       png_int_32 x_offset; /* x offset on page */
       png_int_32 y_offset; /* y offset on page */
       png_byte offset_unit_type; /* offset units type */
    #endif

    #ifdef PNG_pHYs_SUPPORTED
       /* The pHYs chunk gives the physical pixel density of the image for
        * display or printing in "phys_unit_type" units (see PNG_RESOLUTION_
        * defines below).  Data is valid if (valid & PNG_INFO_pHYs) is non-zero.
        */
       png_uint_32 x_pixels_per_unit; /* horizontal pixel density */
       png_uint_32 y_pixels_per_unit; /* vertical pixel density */
       png_byte phys_unit_type; /* resolution type (see PNG_RESOLUTION_ below) */
    #endif

    #ifdef PNG_hIST_SUPPORTED
       /* The hIST chunk contains the relative frequency or importance of the
        * various palette entries, so that a viewer can intelligently select a
        * reduced-color palette, if required.  Data is an array of "num_palette"
        * values in the range [0,65535]. Data valid if (valid & PNG_INFO_hIST)
        * is non-zero.
        */
       png_uint_16p hist;
    #endif

    #ifdef PNG_pCAL_SUPPORTED
       /* The pCAL chunk describes a transformation between the stored pixel
        * values and original physical data values used to create the image.
        * The integer range [0, 2^bit_depth - 1] maps to the floating-point
        * range given by [pcal_X0, pcal_X1], and are further transformed by a
        * (possibly non-linear) transformation function given by "pcal_type"
        * and "pcal_params" into "pcal_units".  Please see the PNG_EQUATION_
        * defines below, and the PNG-Group's PNG extensions document for a
        * complete description of the transformations and how they should be
        * implemented, and for a description of the ASCII parameter strings.
        * Data values are valid if (valid & PNG_INFO_pCAL) non-zero.
        */
       png_charp pcal_purpose;  /* pCAL chunk description string */
       png_int_32 pcal_X0;      /* minimum value */
       png_int_32 pcal_X1;      /* maximum value */
       png_charp pcal_units;    /* Latin-1 string giving physical units */
       png_charpp pcal_params;  /* ASCII strings containing parameter values */
       png_byte pcal_type;      /* equation type (see PNG_EQUATION_ below) */
       png_byte pcal_nparams;   /* number of parameters given in pcal_params */
    #endif

    /* New members added in libpng-1.0.6 */
       png_uint_32 free_me;     /* flags items libpng is responsible for freeing */

    #ifdef PNG_STORE_UNKNOWN_CHUNKS_SUPPORTED
       /* Storage for unknown chunks that the library doesn't recognize. */
       png_unknown_chunkp unknown_chunks;

       /* The type of this field is limited by the type of
        * png_struct::user_chunk_cache_max, else overflow can occur.
        */
       int                unknown_chunks_num;
    #endif

    #ifdef PNG_sPLT_SUPPORTED
       /* Data on sPLT chunks (there may be more than one). */
       png_sPLT_tp splt_palettes;
       int         splt_palettes_num; /* Match type returned by png_get API */
    #endif

    #ifdef PNG_sCAL_SUPPORTED
       /* The sCAL chunk describes the actual physical dimensions of the
        * subject matter of the graphic.  The chunk contains a unit specification
        * a byte value, and two ASCII strings representing floating-point
        * values.  The values are width and height corresponsing to one pixel
        * in the image.  Data values are valid if (valid & PNG_INFO_sCAL) is
        * non-zero.
        */
       png_byte scal_unit;         /* unit of physical scale */
       png_charp scal_s_width;     /* string containing height */
       png_charp scal_s_height;    /* string containing width */
    #endif

    #ifdef PNG_INFO_IMAGE_SUPPORTED
       /* Memory has been allocated if (valid & PNG_ALLOCATED_INFO_ROWS)
          non-zero */
       /* Data valid if (valid & PNG_INFO_IDAT) non-zero */
       png_bytepp row_pointers;        /* the image bits */
    #endif

    };
    #endif /* PNGINFO_H */