    /* pngwrite.c - general routines to write a PNG file
     *
     * Last changed in libpng 1.6.2 [April 25, 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.
     * For conditions of distribution and use, see the disclaimer
     * and license in png.h
     */

    #include "pngpriv.h"
    #if defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
    #  include <errno.h>
    #endif

    #ifdef PNG_WRITE_SUPPORTED

    #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
    /* Write out all the unknown chunks for the current given location */
    static void
    write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,
       unsigned int where)
    {
       if (info_ptr->unknown_chunks_num)
       {
          png_const_unknown_chunkp up;

          png_debug(5, "writing extra chunks");

          for (up = info_ptr->unknown_chunks;
               up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
               ++up)
             if (up->location & where)
          {
             /* If per-chunk unknown chunk handling is enabled use it, otherwise
              * just write the chunks the application has set.
              */
    #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
             int keep = png_handle_as_unknown(png_ptr, up->name);

             /* NOTE: this code is radically different from the read side in the
              * matter of handling an ancillary unknown chunk.  In the read side
              * the default behavior is to discard it, in the code below the default
              * behavior is to write it.  Critical chunks are, however, only
              * written if explicitly listed or if the default is set to write all
              * unknown chunks.
              *
              * The default handling is also slightly weird - it is not possible to
              * stop the writing of all unsafe-to-copy chunks!
              *
              * TODO: REVIEW: this would seem to be a bug.
              */
             if (keep != PNG_HANDLE_CHUNK_NEVER &&
                 ((up->name[3] & 0x20) /* safe-to-copy overrides everything */ ||
                  keep == PNG_HANDLE_CHUNK_ALWAYS ||
                  (keep == PNG_HANDLE_CHUNK_AS_DEFAULT &&
                   png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS)))
    #endif
             {
                /* TODO: review, what is wrong with a zero length unknown chunk? */
                if (up->size == 0)
                   png_warning(png_ptr, "Writing zero-length unknown chunk");

                png_write_chunk(png_ptr, up->name, up->data, up->size);
             }
          }
       }
    }
    #endif /* PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED */

    /* Writes all the PNG information.  This is the suggested way to use the
     * library.  If you have a new chunk to add, make a function to write it,
     * and put it in the correct location here.  If you want the chunk written
     * after the image data, put it in png_write_end().  I strongly encourage
     * you to supply a PNG_INFO_ flag, and check info_ptr->valid before writing
     * the chunk, as that will keep the code from breaking if you want to just
     * write a plain PNG file.  If you have long comments, I suggest writing
     * them in png_write_end(), and compressing them.
     */
    void PNGAPI
    png_write_info_before_PLTE(png_structrp png_ptr, png_const_inforp info_ptr)
    {
       png_debug(1, "in png_write_info_before_PLTE");

       if (png_ptr == NULL || info_ptr == NULL)
          return;

       if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
       {
       /* Write PNG signature */
       png_write_sig(png_ptr);

    #ifdef PNG_MNG_FEATURES_SUPPORTED
       if ((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE) && \
           (png_ptr->mng_features_permitted))
       {
          png_warning(png_ptr, "MNG features are not allowed in a PNG datastream");
          png_ptr->mng_features_permitted = 0;
       }
    #endif

       /* Write IHDR information. */
       png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
           info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
           info_ptr->filter_type,
    #ifdef PNG_WRITE_INTERLACING_SUPPORTED
           info_ptr->interlace_type
    #else
           0
    #endif
          );

       /* The rest of these check to see if the valid field has the appropriate
        * flag set, and if it does, writes the chunk.
        *
        * 1.6.0: COLORSPACE support controls the writing of these chunks too, and
        * the chunks will be written if the WRITE routine is there and information
        * is available in the COLORSPACE.  (See png_colorspace_sync_info in png.c
        * for where the valid flags get set.)
        *
        * Under certain circumstances the colorspace can be invalidated without
        * syncing the info_struct 'valid' flags; this happens if libpng detects and
        * error and calls png_error while the color space is being set, yet the
        * application continues writing the PNG.  So check the 'invalid' flag here
        * too.
        */
    #ifdef PNG_GAMMA_SUPPORTED
    #  ifdef PNG_WRITE_gAMA_SUPPORTED
          if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) &&
             (info_ptr->valid & PNG_INFO_gAMA))
             png_write_gAMA_fixed(png_ptr, info_ptr->colorspace.gamma);
    #  endif
    #endif

    #ifdef PNG_COLORSPACE_SUPPORTED
       /* Write only one of sRGB or an ICC profile.  If a profile was supplied
        * and it matches one of the known sRGB ones issue a warning.
        */
    #  ifdef PNG_WRITE_iCCP_SUPPORTED
          if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
             (info_ptr->valid & PNG_INFO_iCCP))
          {
    #        ifdef PNG_WRITE_sRGB_SUPPORTED
                if (info_ptr->valid & PNG_INFO_sRGB)
                   png_app_warning(png_ptr,
                      "profile matches sRGB but writing iCCP instead");
    #        endif

             png_write_iCCP(png_ptr, info_ptr->iccp_name,
                info_ptr->iccp_profile);
          }
    #     ifdef PNG_WRITE_sRGB_SUPPORTED
             else
    #     endif
    #  endif

    #  ifdef PNG_WRITE_sRGB_SUPPORTED
          if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
             (info_ptr->valid & PNG_INFO_sRGB))
             png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);
    #  endif /* WRITE_sRGB */
    #endif /* COLORSPACE */

    #ifdef PNG_WRITE_sBIT_SUPPORTED
       if (info_ptr->valid & PNG_INFO_sBIT)
          png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
    #endif

    #ifdef PNG_COLORSPACE_SUPPORTED
    #  ifdef PNG_WRITE_cHRM_SUPPORTED
          if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&
             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) &&
             (info_ptr->valid & PNG_INFO_cHRM))
             png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);
    #  endif
    #endif

    #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
          write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
    #endif

          png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;
       }
    }

    void PNGAPI
    png_write_info(png_structrp png_ptr, png_const_inforp info_ptr)
    {
    #if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
       int i;
    #endif

       png_debug(1, "in png_write_info");

       if (png_ptr == NULL || info_ptr == NULL)
          return;

       png_write_info_before_PLTE(png_ptr, info_ptr);

       if (info_ptr->valid & PNG_INFO_PLTE)
          png_write_PLTE(png_ptr, info_ptr->palette,
              (png_uint_32)info_ptr->num_palette);

       else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
          png_error(png_ptr, "Valid palette required for paletted images");

    #ifdef PNG_WRITE_tRNS_SUPPORTED
       if (info_ptr->valid & PNG_INFO_tRNS)
       {
    #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
          /* Invert the alpha channel (in tRNS) */
          if ((png_ptr->transformations & PNG_INVERT_ALPHA) &&
              info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
          {
             int j;
             for (j = 0; j<(int)info_ptr->num_trans; j++)
                info_ptr->trans_alpha[j] =
                   (png_byte)(255 - info_ptr->trans_alpha[j]);
          }
    #endif
          png_write_tRNS(png_ptr, info_ptr->trans_alpha, &(info_ptr->trans_color),
              info_ptr->num_trans, info_ptr->color_type);
       }
    #endif
    #ifdef PNG_WRITE_bKGD_SUPPORTED
       if (info_ptr->valid & PNG_INFO_bKGD)
          png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
    #endif

    #ifdef PNG_WRITE_hIST_SUPPORTED
       if (info_ptr->valid & PNG_INFO_hIST)
          png_write_hIST(png_ptr, info_ptr->hist, info_ptr->num_palette);
    #endif

    #ifdef PNG_WRITE_oFFs_SUPPORTED
       if (info_ptr->valid & PNG_INFO_oFFs)
          png_write_oFFs(png_ptr, info_ptr->x_offset, info_ptr->y_offset,
              info_ptr->offset_unit_type);
    #endif

    #ifdef PNG_WRITE_pCAL_SUPPORTED
       if (info_ptr->valid & PNG_INFO_pCAL)
          png_write_pCAL(png_ptr, info_ptr->pcal_purpose, info_ptr->pcal_X0,
              info_ptr->pcal_X1, info_ptr->pcal_type, info_ptr->pcal_nparams,
              info_ptr->pcal_units, info_ptr->pcal_params);
    #endif

    #ifdef PNG_WRITE_sCAL_SUPPORTED
       if (info_ptr->valid & PNG_INFO_sCAL)
          png_write_sCAL_s(png_ptr, (int)info_ptr->scal_unit,
              info_ptr->scal_s_width, info_ptr->scal_s_height);
    #endif /* sCAL */

    #ifdef PNG_WRITE_pHYs_SUPPORTED
       if (info_ptr->valid & PNG_INFO_pHYs)
          png_write_pHYs(png_ptr, info_ptr->x_pixels_per_unit,
              info_ptr->y_pixels_per_unit, info_ptr->phys_unit_type);
    #endif /* pHYs */

    #ifdef PNG_WRITE_tIME_SUPPORTED
       if (info_ptr->valid & PNG_INFO_tIME)
       {
          png_write_tIME(png_ptr, &(info_ptr->mod_time));
          png_ptr->mode |= PNG_WROTE_tIME;
       }
    #endif /* tIME */

    #ifdef PNG_WRITE_sPLT_SUPPORTED
       if (info_ptr->valid & PNG_INFO_sPLT)
          for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
             png_write_sPLT(png_ptr, info_ptr->splt_palettes + i);
    #endif /* sPLT */

    #ifdef PNG_WRITE_TEXT_SUPPORTED
       /* Check to see if we need to write text chunks */
       for (i = 0; i < info_ptr->num_text; i++)
       {
          png_debug2(2, "Writing header text chunk %d, type %d", i,
              info_ptr->text[i].compression);
          /* An internationalized chunk? */
          if (info_ptr->text[i].compression > 0)
          {
    #ifdef PNG_WRITE_iTXt_SUPPORTED
             /* Write international chunk */
             png_write_iTXt(png_ptr,
                 info_ptr->text[i].compression,
                 info_ptr->text[i].key,
                 info_ptr->text[i].lang,
                 info_ptr->text[i].lang_key,
                 info_ptr->text[i].text);
    #else
              png_warning(png_ptr, "Unable to write international text");
    #endif
              /* Mark this chunk as written */
              info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
          }

          /* If we want a compressed text chunk */
          else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_zTXt)
          {
    #ifdef PNG_WRITE_zTXt_SUPPORTED
             /* Write compressed chunk */
             png_write_zTXt(png_ptr, info_ptr->text[i].key,
                 info_ptr->text[i].text, 0,
                 info_ptr->text[i].compression);
    #else
             png_warning(png_ptr, "Unable to write compressed text");
    #endif
             /* Mark this chunk as written */
             info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
          }

          else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
          {
    #ifdef PNG_WRITE_tEXt_SUPPORTED
             /* Write uncompressed chunk */
             png_write_tEXt(png_ptr, info_ptr->text[i].key,
                 info_ptr->text[i].text,
                 0);
             /* Mark this chunk as written */
             info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
    #else
             /* Can't get here */
             png_warning(png_ptr, "Unable to write uncompressed text");
    #endif
          }
       }
    #endif /* tEXt */

    #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
       write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);
    #endif
    }

    /* Writes the end of the PNG file.  If you don't want to write comments or
     * time information, you can pass NULL for info.  If you already wrote these
     * in png_write_info(), do not write them again here.  If you have long
     * comments, I suggest writing them here, and compressing them.
     */
    void PNGAPI
    png_write_end(png_structrp png_ptr, png_inforp info_ptr)
    {
       png_debug(1, "in png_write_end");

       if (png_ptr == NULL)
          return;

       if (!(png_ptr->mode & PNG_HAVE_IDAT))
          png_error(png_ptr, "No IDATs written into file");

    #ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
       if (png_ptr->num_palette_max > png_ptr->num_palette)
          png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");
    #endif

       /* See if user wants us to write information chunks */
       if (info_ptr != NULL)
       {
    #ifdef PNG_WRITE_TEXT_SUPPORTED
          int i; /* local index variable */
    #endif
    #ifdef PNG_WRITE_tIME_SUPPORTED
          /* Check to see if user has supplied a time chunk */
          if ((info_ptr->valid & PNG_INFO_tIME) &&
              !(png_ptr->mode & PNG_WROTE_tIME))
             png_write_tIME(png_ptr, &(info_ptr->mod_time));

    #endif
    #ifdef PNG_WRITE_TEXT_SUPPORTED
          /* Loop through comment chunks */
          for (i = 0; i < info_ptr->num_text; i++)
          {
             png_debug2(2, "Writing trailer text chunk %d, type %d", i,
                info_ptr->text[i].compression);
             /* An internationalized chunk? */
             if (info_ptr->text[i].compression > 0)
             {
    #ifdef PNG_WRITE_iTXt_SUPPORTED
                /* Write international chunk */
                png_write_iTXt(png_ptr,
                    info_ptr->text[i].compression,
                    info_ptr->text[i].key,
                    info_ptr->text[i].lang,
                    info_ptr->text[i].lang_key,
                    info_ptr->text[i].text);
    #else
                png_warning(png_ptr, "Unable to write international text");
    #endif
                /* Mark this chunk as written */
                info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
             }

             else if (info_ptr->text[i].compression >= PNG_TEXT_COMPRESSION_zTXt)
             {
    #ifdef PNG_WRITE_zTXt_SUPPORTED
                /* Write compressed chunk */
                png_write_zTXt(png_ptr, info_ptr->text[i].key,
                    info_ptr->text[i].text, 0,
                    info_ptr->text[i].compression);
    #else
                png_warning(png_ptr, "Unable to write compressed text");
    #endif
                /* Mark this chunk as written */
                info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
             }

             else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
             {
    #ifdef PNG_WRITE_tEXt_SUPPORTED
                /* Write uncompressed chunk */
                png_write_tEXt(png_ptr, info_ptr->text[i].key,
                    info_ptr->text[i].text, 0);
    #else
                png_warning(png_ptr, "Unable to write uncompressed text");
    #endif

                /* Mark this chunk as written */
                info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
             }
          }
    #endif
    #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
          write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);
    #endif
       }

       png_ptr->mode |= PNG_AFTER_IDAT;

       /* Write end of PNG file */
       png_write_IEND(png_ptr);
       /* This flush, added in libpng-1.0.8, removed from libpng-1.0.9beta03,
        * and restored again in libpng-1.2.30, may cause some applications that
        * do not set png_ptr->output_flush_fn to crash.  If your application
        * experiences a problem, please try building libpng with
        * PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED defined, and report the event to
        * png-mng-implement at lists.sf.net .
        */
    #ifdef PNG_WRITE_FLUSH_SUPPORTED
    #  ifdef PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED
       png_flush(png_ptr);
    #  endif
    #endif
    }

    #ifdef PNG_CONVERT_tIME_SUPPORTED
    void PNGAPI
    png_convert_from_struct_tm(png_timep ptime, PNG_CONST struct tm * ttime)
    {
       png_debug(1, "in png_convert_from_struct_tm");

       ptime->year = (png_uint_16)(1900 + ttime->tm_year);
       ptime->month = (png_byte)(ttime->tm_mon + 1);
       ptime->day = (png_byte)ttime->tm_mday;
       ptime->hour = (png_byte)ttime->tm_hour;
       ptime->minute = (png_byte)ttime->tm_min;
       ptime->second = (png_byte)ttime->tm_sec;
    }

    void PNGAPI
    png_convert_from_time_t(png_timep ptime, time_t ttime)
    {
       struct tm *tbuf;

       png_debug(1, "in png_convert_from_time_t");

       tbuf = gmtime(&ttime);
       png_convert_from_struct_tm(ptime, tbuf);
    }
    #endif

    /* Initialize png_ptr structure, and allocate any memory needed */
    PNG_FUNCTION(png_structp,PNGAPI
    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)
    {
    #ifndef PNG_USER_MEM_SUPPORTED
       png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
          error_fn, warn_fn, NULL, NULL, NULL);
    #else
       return png_create_write_struct_2(user_png_ver, error_ptr, error_fn,
           warn_fn, NULL, NULL, NULL);
    }

    /* Alternate initialize png_ptr structure, and allocate any memory needed */
    PNG_FUNCTION(png_structp,PNGAPI
    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)
    {
       png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,
          error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);
    #endif /* PNG_USER_MEM_SUPPORTED */
       if (png_ptr != NULL)
       {
          /* Set the zlib control values to defaults; they can be overridden by the
           * application after the struct has been created.
           */
          png_ptr->zbuffer_size = PNG_ZBUF_SIZE;

          /* The 'zlib_strategy' setting is irrelevant because png_default_claim in
           * pngwutil.c defaults it according to whether or not filters will be
           * used, and ignores this setting.
           */
          png_ptr->zlib_strategy = PNG_Z_DEFAULT_STRATEGY;
          png_ptr->zlib_level = PNG_Z_DEFAULT_COMPRESSION;
          png_ptr->zlib_mem_level = 8;
          png_ptr->zlib_window_bits = 15;
          png_ptr->zlib_method = 8;

    #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED
          png_ptr->zlib_text_strategy = PNG_TEXT_Z_DEFAULT_STRATEGY;
          png_ptr->zlib_text_level = PNG_TEXT_Z_DEFAULT_COMPRESSION;
          png_ptr->zlib_text_mem_level = 8;
          png_ptr->zlib_text_window_bits = 15;
          png_ptr->zlib_text_method = 8;
    #endif /* PNG_WRITE_COMPRESSED_TEXT_SUPPORTED */

          /* This is a highly dubious configuration option; by default it is off,
           * but it may be appropriate for private builds that are testing
           * extensions not conformant to the current specification, or of
           * applications that must not fail to write at all costs!
           */
    #ifdef PNG_BENIGN_WRITE_ERRORS_SUPPORTED
          png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
          /* In stable builds only warn if an application error can be completely
           * handled.
           */
    #endif

          /* App warnings are warnings in release (or release candidate) builds but
           * are errors during development.
           */
    #if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC
          png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;
    #endif

          /* TODO: delay this, it can be done in png_init_io() (if the app doesn't
           * do it itself) avoiding setting the default function if it is not
           * required.
           */
          png_set_write_fn(png_ptr, NULL, NULL, NULL);
       }

       return png_ptr;
    }

    /* Write a few rows of image data.  If the image is interlaced,
     * either you will have to write the 7 sub images, or, if you
     * have called png_set_interlace_handling(), you will have to
     * "write" the image seven times.
     */
    void PNGAPI
    png_write_rows(png_structrp png_ptr, png_bytepp row,
        png_uint_32 num_rows)
    {
       png_uint_32 i; /* row counter */
       png_bytepp rp; /* row pointer */

       png_debug(1, "in png_write_rows");

       if (png_ptr == NULL)
          return;

       /* Loop through the rows */
       for (i = 0, rp = row; i < num_rows; i++, rp++)
       {
          png_write_row(png_ptr, *rp);
       }
    }

    /* Write the image.  You only need to call this function once, even
     * if you are writing an interlaced image.
     */
    void PNGAPI
    png_write_image(png_structrp png_ptr, png_bytepp image)
    {
       png_uint_32 i; /* row index */
       int pass, num_pass; /* pass variables */
       png_bytepp rp; /* points to current row */

       if (png_ptr == NULL)
          return;

       png_debug(1, "in png_write_image");

    #ifdef PNG_WRITE_INTERLACING_SUPPORTED
       /* Initialize interlace handling.  If image is not interlaced,
        * this will set pass to 1
        */
       num_pass = png_set_interlace_handling(png_ptr);
    #else
       num_pass = 1;
    #endif
       /* Loop through passes */
       for (pass = 0; pass < num_pass; pass++)
       {
          /* Loop through image */
          for (i = 0, rp = image; i < png_ptr->height; i++, rp++)
          {
             png_write_row(png_ptr, *rp);
          }
       }
    }

    /* Called by user to write a row of image data */
    void PNGAPI
    png_write_row(png_structrp png_ptr, png_const_bytep row)
    {
       /* 1.5.6: moved from png_struct to be a local structure: */
       png_row_info row_info;

       if (png_ptr == NULL)
          return;

       png_debug2(1, "in png_write_row (row %u, pass %d)",
          png_ptr->row_number, png_ptr->pass);

       /* Initialize transformations and other stuff if first time */
       if (png_ptr->row_number == 0 && png_ptr->pass == 0)
       {
          /* Make sure we wrote the header info */
          if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
             png_error(png_ptr,
                 "png_write_info was never called before png_write_row");

          /* Check for transforms that have been set but were defined out */
    #if !defined(PNG_WRITE_INVERT_SUPPORTED) && defined(PNG_READ_INVERT_SUPPORTED)
          if (png_ptr->transformations & PNG_INVERT_MONO)
             png_warning(png_ptr, "PNG_WRITE_INVERT_SUPPORTED is not defined");
    #endif

    #if !defined(PNG_WRITE_FILLER_SUPPORTED) && defined(PNG_READ_FILLER_SUPPORTED)
          if (png_ptr->transformations & PNG_FILLER)
             png_warning(png_ptr, "PNG_WRITE_FILLER_SUPPORTED is not defined");
    #endif
    #if !defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
        defined(PNG_READ_PACKSWAP_SUPPORTED)
          if (png_ptr->transformations & PNG_PACKSWAP)
             png_warning(png_ptr,
                 "PNG_WRITE_PACKSWAP_SUPPORTED is not defined");
    #endif

    #if !defined(PNG_WRITE_PACK_SUPPORTED) && defined(PNG_READ_PACK_SUPPORTED)
          if (png_ptr->transformations & PNG_PACK)
             png_warning(png_ptr, "PNG_WRITE_PACK_SUPPORTED is not defined");
    #endif

    #if !defined(PNG_WRITE_SHIFT_SUPPORTED) && defined(PNG_READ_SHIFT_SUPPORTED)
          if (png_ptr->transformations & PNG_SHIFT)
             png_warning(png_ptr, "PNG_WRITE_SHIFT_SUPPORTED is not defined");
    #endif

    #if !defined(PNG_WRITE_BGR_SUPPORTED) && defined(PNG_READ_BGR_SUPPORTED)
          if (png_ptr->transformations & PNG_BGR)
             png_warning(png_ptr, "PNG_WRITE_BGR_SUPPORTED is not defined");
    #endif

    #if !defined(PNG_WRITE_SWAP_SUPPORTED) && defined(PNG_READ_SWAP_SUPPORTED)
          if (png_ptr->transformations & PNG_SWAP_BYTES)
             png_warning(png_ptr, "PNG_WRITE_SWAP_SUPPORTED is not defined");
    #endif

          png_write_start_row(png_ptr);
       }

    #ifdef PNG_WRITE_INTERLACING_SUPPORTED
       /* If interlaced and not interested in row, return */
       if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
       {
          switch (png_ptr->pass)
          {
             case 0:
                if (png_ptr->row_number & 0x07)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 1:
                if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 2:
                if ((png_ptr->row_number & 0x07) != 4)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 3:
                if ((png_ptr->row_number & 0x03) || png_ptr->width < 3)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 4:
                if ((png_ptr->row_number & 0x03) != 2)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 5:
                if ((png_ptr->row_number & 0x01) || png_ptr->width < 2)
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             case 6:
                if (!(png_ptr->row_number & 0x01))
                {
                   png_write_finish_row(png_ptr);
                   return;
                }
                break;

             default: /* error: ignore it */
                break;
          }
       }
    #endif

       /* Set up row info for transformations */
       row_info.color_type = png_ptr->color_type;
       row_info.width = png_ptr->usr_width;
       row_info.channels = png_ptr->usr_channels;
       row_info.bit_depth = png_ptr->usr_bit_depth;
       row_info.pixel_depth = (png_byte)(row_info.bit_depth * row_info.channels);
       row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);

       png_debug1(3, "row_info->color_type = %d", row_info.color_type);
       png_debug1(3, "row_info->width = %u", row_info.width);
       png_debug1(3, "row_info->channels = %d", row_info.channels);
       png_debug1(3, "row_info->bit_depth = %d", row_info.bit_depth);
       png_debug1(3, "row_info->pixel_depth = %d", row_info.pixel_depth);
       png_debug1(3, "row_info->rowbytes = %lu", (unsigned long)row_info.rowbytes);

       /* Copy user's row into buffer, leaving room for filter byte. */
       memcpy(png_ptr->row_buf + 1, row, row_info.rowbytes);

    #ifdef PNG_WRITE_INTERLACING_SUPPORTED
       /* Handle interlacing */
       if (png_ptr->interlaced && png_ptr->pass < 6 &&
           (png_ptr->transformations & PNG_INTERLACE))
       {
          png_do_write_interlace(&row_info, png_ptr->row_buf + 1, png_ptr->pass);
          /* This should always get caught above, but still ... */
          if (!(row_info.width))
          {
             png_write_finish_row(png_ptr);
             return;
          }
       }
    #endif

    #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
       /* Handle other transformations */
       if (png_ptr->transformations)
          png_do_write_transformations(png_ptr, &row_info);
    #endif

       /* At this point the row_info pixel depth must match the 'transformed' depth,
        * which is also the output depth.
        */
       if (row_info.pixel_depth != png_ptr->pixel_depth ||
          row_info.pixel_depth != png_ptr->transformed_pixel_depth)
          png_error(png_ptr, "internal write transform logic error");

    #ifdef PNG_MNG_FEATURES_SUPPORTED
       /* Write filter_method 64 (intrapixel differencing) only if
        * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
        * 2. Libpng did not write a PNG signature (this filter_method is only
        *    used in PNG datastreams that are embedded in MNG datastreams) and
        * 3. The application called png_permit_mng_features with a mask that
        *    included PNG_FLAG_MNG_FILTER_64 and
        * 4. The filter_method is 64 and
        * 5. The color_type is RGB or RGBA
        */
       if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
           (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
       {
          /* Intrapixel differencing */
          png_do_write_intrapixel(&row_info, png_ptr->row_buf + 1);
       }
    #endif

    /* Added at libpng-1.5.10 */
    #ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
       /* Check for out-of-range palette index */
       if (row_info.color_type == PNG_COLOR_TYPE_PALETTE &&
           png_ptr->num_palette_max >= 0)
          png_do_check_palette_indexes(png_ptr, &row_info);
    #endif

       /* Find a filter if necessary, filter the row and write it out. */
       png_write_find_filter(png_ptr, &row_info);

       if (png_ptr->write_row_fn != NULL)
          (*(png_ptr->write_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
    }

    #ifdef PNG_WRITE_FLUSH_SUPPORTED
    /* Set the automatic flush interval or 0 to turn flushing off */
    void PNGAPI
    png_set_flush(png_structrp png_ptr, int nrows)
    {
       png_debug(1, "in png_set_flush");

       if (png_ptr == NULL)
          return;

       png_ptr->flush_dist = (nrows < 0 ? 0 : nrows);
    }

    /* Flush the current output buffers now */
    void PNGAPI
    png_write_flush(png_structrp png_ptr)
    {
       png_debug(1, "in png_write_flush");

       if (png_ptr == NULL)
          return;

       /* We have already written out all of the data */
       if (png_ptr->row_number >= png_ptr->num_rows)
          return;

       png_compress_IDAT(png_ptr, NULL, 0, Z_SYNC_FLUSH);
       png_ptr->flush_rows = 0;
       png_flush(png_ptr);
    }
    #endif /* PNG_WRITE_FLUSH_SUPPORTED */

    #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
    static void png_reset_filter_heuristics(png_structrp png_ptr);/* forward decl */
    #endif

    /* Free any memory used in png_ptr struct without freeing the struct itself. */
    static void
    png_write_destroy(png_structrp png_ptr)
    {
       png_debug(1, "in png_write_destroy");

       /* Free any memory zlib uses */
       if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)
          deflateEnd(&png_ptr->zstream);

       /* Free our memory.  png_free checks NULL for us. */
       png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);
       png_free(png_ptr, png_ptr->row_buf);
    #ifdef PNG_WRITE_FILTER_SUPPORTED
       png_free(png_ptr, png_ptr->prev_row);
       png_free(png_ptr, png_ptr->sub_row);
       png_free(png_ptr, png_ptr->up_row);
       png_free(png_ptr, png_ptr->avg_row);
       png_free(png_ptr, png_ptr->paeth_row);
    #endif

    #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
       /* Use this to save a little code space, it doesn't free the filter_costs */
       png_reset_filter_heuristics(png_ptr);
       png_free(png_ptr, png_ptr->filter_costs);
       png_free(png_ptr, png_ptr->inv_filter_costs);
    #endif

    #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
       png_free(png_ptr, png_ptr->chunk_list);
    #endif

       /* The error handling and memory handling information is left intact at this
        * point: the jmp_buf may still have to be freed.  See png_destroy_png_struct
        * for how this happens.
        */
    }

    /* Free all memory used by the write.
     * In libpng 1.6.0 this API changed quietly to no longer accept a NULL value for
     * *png_ptr_ptr.  Prior to 1.6.0 it would accept such a value and it would free
     * the passed in info_structs but it would quietly fail to free any of the data
     * inside them.  In 1.6.0 it quietly does nothing (it has to be quiet because it
     * has no png_ptr.)
     */
    void PNGAPI
    png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
    {
       png_debug(1, "in png_destroy_write_struct");

       if (png_ptr_ptr != NULL)
       {
          png_structrp png_ptr = *png_ptr_ptr;

          if (png_ptr != NULL) /* added in libpng 1.6.0 */
          {
             png_destroy_info_struct(png_ptr, info_ptr_ptr);

             *png_ptr_ptr = NULL;
             png_write_destroy(png_ptr);
             png_destroy_png_struct(png_ptr);
          }
       }
    }

    /* Allow the application to select one or more row filters to use. */
    void PNGAPI
    png_set_filter(png_structrp png_ptr, int method, int filters)
    {
       png_debug(1, "in png_set_filter");

       if (png_ptr == NULL)
          return;

    #ifdef PNG_MNG_FEATURES_SUPPORTED
       if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
           (method == PNG_INTRAPIXEL_DIFFERENCING))
          method = PNG_FILTER_TYPE_BASE;

    #endif
       if (method == PNG_FILTER_TYPE_BASE)
       {
          switch (filters & (PNG_ALL_FILTERS | 0x07))
          {
    #ifdef PNG_WRITE_FILTER_SUPPORTED
             case 5:
             case 6:
             case 7: png_app_error(png_ptr, "Unknown row filter for method 0");
                /* FALL THROUGH */
    #endif /* PNG_WRITE_FILTER_SUPPORTED */
             case PNG_FILTER_VALUE_NONE:
                png_ptr->do_filter = PNG_FILTER_NONE; break;

    #ifdef PNG_WRITE_FILTER_SUPPORTED
             case PNG_FILTER_VALUE_SUB:
                png_ptr->do_filter = PNG_FILTER_SUB; break;

             case PNG_FILTER_VALUE_UP:
                png_ptr->do_filter = PNG_FILTER_UP; break;

             case PNG_FILTER_VALUE_AVG:
                png_ptr->do_filter = PNG_FILTER_AVG; break;

             case PNG_FILTER_VALUE_PAETH:
                png_ptr->do_filter = PNG_FILTER_PAETH; break;

             default:
                png_ptr->do_filter = (png_byte)filters; break;
    #else
             default:
                png_app_error(png_ptr, "Unknown row filter for method 0");
    #endif /* PNG_WRITE_FILTER_SUPPORTED */
          }

          /* If we have allocated the row_buf, this means we have already started
           * with the image and we should have allocated all of the filter buffers
           * that have been selected.  If prev_row isn't already allocated, then
           * it is too late to start using the filters that need it, since we
           * will be missing the data in the previous row.  If an application
           * wants to start and stop using particular filters during compression,
           * it should start out with all of the filters, and then add and
           * remove them after the start of compression.
           */
          if (png_ptr->row_buf != NULL)
          {
    #ifdef PNG_WRITE_FILTER_SUPPORTED
             if ((png_ptr->do_filter & PNG_FILTER_SUB) && png_ptr->sub_row == NULL)
             {
                png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
                    (png_ptr->rowbytes + 1));
                png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
             }

             if ((png_ptr->do_filter & PNG_FILTER_UP) && png_ptr->up_row == NULL)
             {
                if (png_ptr->prev_row == NULL)
                {
                   png_warning(png_ptr, "Can't add Up filter after starting");
                   png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                       ~PNG_FILTER_UP);
                }

                else
                {
                   png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
                       (png_ptr->rowbytes + 1));
                   png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
                }
             }

             if ((png_ptr->do_filter & PNG_FILTER_AVG) && png_ptr->avg_row == NULL)
             {
                if (png_ptr->prev_row == NULL)
                {
                   png_warning(png_ptr, "Can't add Average filter after starting");
                   png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                       ~PNG_FILTER_AVG);
                }

                else
                {
                   png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
                       (png_ptr->rowbytes + 1));
                   png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
                }
             }

             if ((png_ptr->do_filter & PNG_FILTER_PAETH) &&
                 png_ptr->paeth_row == NULL)
             {
                if (png_ptr->prev_row == NULL)
                {
                   png_warning(png_ptr, "Can't add Paeth filter after starting");
                   png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
                }

                else
                {
                   png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
                       (png_ptr->rowbytes + 1));
                   png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
                }
             }

             if (png_ptr->do_filter == PNG_NO_FILTERS)
    #endif /* PNG_WRITE_FILTER_SUPPORTED */
                png_ptr->do_filter = PNG_FILTER_NONE;
          }
       }
       else
          png_error(png_ptr, "Unknown custom filter method");
    }

    /* This allows us to influence the way in which libpng chooses the "best"
     * filter for the current scanline.  While the "minimum-sum-of-absolute-
     * differences metric is relatively fast and effective, there is some
     * question as to whether it can be improved upon by trying to keep the
     * filtered data going to zlib more consistent, hopefully resulting in
     * better compression.
     */
    #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
    /* Convenience reset API. */
    static void
    png_reset_filter_heuristics(png_structrp png_ptr)
    {
       /* Clear out any old values in the 'weights' - this must be done because if
        * the app calls set_filter_heuristics multiple times with different
        * 'num_weights' values we would otherwise potentially have wrong sized
        * arrays.
        */
       png_ptr->num_prev_filters = 0;
       png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
       if (png_ptr->prev_filters != NULL)
       {
          png_bytep old = png_ptr->prev_filters;
          png_ptr->prev_filters = NULL;
          png_free(png_ptr, old);
       }
       if (png_ptr->filter_weights != NULL)
       {
          png_uint_16p old = png_ptr->filter_weights;
          png_ptr->filter_weights = NULL;
          png_free(png_ptr, old);
       }

       if (png_ptr->inv_filter_weights != NULL)
       {
          png_uint_16p old = png_ptr->inv_filter_weights;
          png_ptr->inv_filter_weights = NULL;
          png_free(png_ptr, old);
       }

       /* Leave the filter_costs - this array is fixed size. */
    }

    static int
    png_init_filter_heuristics(png_structrp png_ptr, int heuristic_method,
       int num_weights)
    {
       if (png_ptr == NULL)
          return 0;

       /* Clear out the arrays */
       png_reset_filter_heuristics(png_ptr);

       /* Check arguments; the 'reset' function makes the correct settings for the
        * unweighted case, but we must handle the weight case by initializing the
        * arrays for the caller.
        */
       if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int i;

          if (num_weights > 0)
          {
             png_ptr->prev_filters = (png_bytep)png_malloc(png_ptr,
                 (png_uint_32)((sizeof (png_byte)) * num_weights));

             /* To make sure that the weighting starts out fairly */
             for (i = 0; i < num_weights; i++)
             {
                png_ptr->prev_filters[i] = 255;
             }

             png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
                 (png_uint_32)((sizeof (png_uint_16)) * num_weights));

             png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
                 (png_uint_32)((sizeof (png_uint_16)) * num_weights));

             for (i = 0; i < num_weights; i++)
             {
                png_ptr->inv_filter_weights[i] =
                png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
             }

             /* Safe to set this now */
             png_ptr->num_prev_filters = (png_byte)num_weights;
          }

          /* If, in the future, there are other filter methods, this would
           * need to be based on png_ptr->filter.
           */
          if (png_ptr->filter_costs == NULL)
          {
             png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
                 (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));

             png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
                 (png_uint_32)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));
          }

          for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
          {
             png_ptr->inv_filter_costs[i] =
             png_ptr->filter_costs[i] = PNG_COST_FACTOR;
          }

          /* All the arrays are inited, safe to set this: */
          png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_WEIGHTED;

          /* Return the 'ok' code. */
          return 1;
       }
       else if (heuristic_method == PNG_FILTER_HEURISTIC_DEFAULT ||
          heuristic_method == PNG_FILTER_HEURISTIC_UNWEIGHTED)
       {
          return 1;
       }
       else
       {
          png_warning(png_ptr, "Unknown filter heuristic method");
          return 0;
       }
    }

    /* Provide floating and fixed point APIs */
    #ifdef PNG_FLOATING_POINT_SUPPORTED
    void PNGAPI
    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_debug(1, "in png_set_filter_heuristics");

       /* The internal API allocates all the arrays and ensures that the elements of
        * those arrays are set to the default value.
        */
       if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
          return;

       /* If using the weighted method copy in the weights. */
       if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int i;
          for (i = 0; i < num_weights; i++)
          {
             if (filter_weights[i] <= 0.0)
             {
                png_ptr->inv_filter_weights[i] =
                png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
             }

             else
             {
                png_ptr->inv_filter_weights[i] =
                    (png_uint_16)(PNG_WEIGHT_FACTOR*filter_weights[i]+.5);

                png_ptr->filter_weights[i] =
                    (png_uint_16)(PNG_WEIGHT_FACTOR/filter_weights[i]+.5);
             }
          }

          /* Here is where we set the relative costs of the different filters.  We
           * should take the desired compression level into account when setting
           * the costs, so that Paeth, for instance, has a high relative cost at low
           * compression levels, while it has a lower relative cost at higher
           * compression settings.  The filter types are in order of increasing
           * relative cost, so it would be possible to do this with an algorithm.
           */
          for (i = 0; i < PNG_FILTER_VALUE_LAST; i++) if (filter_costs[i] >= 1.0)
          {
             png_ptr->inv_filter_costs[i] =
                 (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);

             png_ptr->filter_costs[i] =
                 (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
          }
       }
    }
    #endif /* FLOATING_POINT */

    #ifdef PNG_FIXED_POINT_SUPPORTED
    void PNGAPI
    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)
    {
       png_debug(1, "in png_set_filter_heuristics_fixed");

       /* The internal API allocates all the arrays and ensures that the elements of
        * those arrays are set to the default value.
        */
       if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
          return;

       /* If using the weighted method copy in the weights. */
       if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
       {
          int i;
          for (i = 0; i < num_weights; i++)
          {
             if (filter_weights[i] <= 0)
             {
                png_ptr->inv_filter_weights[i] =
                png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
             }

             else
             {
                png_ptr->inv_filter_weights[i] = (png_uint_16)
                   ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);

                png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
                   PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
             }
          }

          /* Here is where we set the relative costs of the different filters.  We
           * should take the desired compression level into account when setting
           * the costs, so that Paeth, for instance, has a high relative cost at low
           * compression levels, while it has a lower relative cost at higher
           * compression settings.  The filter types are in order of increasing
           * relative cost, so it would be possible to do this with an algorithm.
           */
          for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
             if (filter_costs[i] >= PNG_FP_1)
          {
             png_uint_32 tmp;

             /* Use a 32 bit unsigned temporary here because otherwise the
              * intermediate value will be a 32 bit *signed* integer (ANSI rules)
              * and this will get the wrong answer on division.
              */
             tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
             tmp /= filter_costs[i];

             png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;

             tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
             tmp /= PNG_FP_1;

             png_ptr->filter_costs[i] = (png_uint_16)tmp;
          }
       }
    }
    #endif /* FIXED_POINT */
    #endif /* PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */

    void PNGAPI
    png_set_compression_level(png_structrp png_ptr, int level)
    {
       png_debug(1, "in png_set_compression_level");

       if (png_ptr == NULL)
          return;

       png_ptr->zlib_level = level;
    }

    void PNGAPI
    png_set_compression_mem_level(png_structrp png_ptr, int mem_level)
    {
       png_debug(1, "in png_set_compression_mem_level");

       if (png_ptr == NULL)
          return;

       png_ptr->zlib_mem_level = mem_level;
    }

    void PNGAPI
    png_set_compression_strategy(png_structrp png_ptr, int strategy)
    {
       png_debug(1, "in png_set_compression_strategy");

       if (png_ptr == NULL)
          return;

       /* The flag setting here prevents the libpng dynamic selection of strategy.
        */
       png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_STRATEGY;
       png_ptr->zlib_strategy = strategy;
    }

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

       /* Prior to 1.6.0 this would warn but then set the window_bits value, this
        * meant that negative window bits values could be selected which would cause
        * libpng to write a non-standard PNG file with raw deflate or gzip
        * compressed IDAT or ancillary chunks.  Such files can be read and there is
        * no warning on read, so this seems like a very bad idea.
        */
       if (window_bits > 15)
       {
          png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
          window_bits = 15;
       }

       else if (window_bits < 8)
       {
          png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
          window_bits = 8;
       }

       png_ptr->zlib_window_bits = window_bits;
    }

    void PNGAPI
    png_set_compression_method(png_structrp png_ptr, int method)
    {
       png_debug(1, "in png_set_compression_method");

       if (png_ptr == NULL)
          return;

       /* This would produce an invalid PNG file if it worked, but it doesn't and
        * deflate will fault it, so it is harmless to just warn here.
        */
       if (method != 8)
          png_warning(png_ptr, "Only compression method 8 is supported by PNG");

       png_ptr->zlib_method = method;
    }

    /* The following were added to libpng-1.5.4 */
    #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
    void PNGAPI
    png_set_text_compression_level(png_structrp png_ptr, int level)
    {
       png_debug(1, "in png_set_text_compression_level");

       if (png_ptr == NULL)
          return;

       png_ptr->zlib_text_level = level;
    }

    void PNGAPI
    png_set_text_compression_mem_level(png_structrp png_ptr, int mem_level)
    {
       png_debug(1, "in png_set_text_compression_mem_level");

       if (png_ptr == NULL)
          return;

       png_ptr->zlib_text_mem_level = mem_level;
    }

    void PNGAPI
    png_set_text_compression_strategy(png_structrp png_ptr, int strategy)
    {
       png_debug(1, "in png_set_text_compression_strategy");

       if (png_ptr == NULL)
          return;

       png_ptr->zlib_text_strategy = strategy;
    }

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

       if (window_bits > 15)
       {
          png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
          window_bits = 15;
       }

       else if (window_bits < 8)
       {
          png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
          window_bits = 8;
       }

       png_ptr->zlib_text_window_bits = window_bits;
    }

    void PNGAPI
    png_set_text_compression_method(png_structrp png_ptr, int method)
    {
       png_debug(1, "in png_set_text_compression_method");

       if (png_ptr == NULL)
          return;

       if (method != 8)
          png_warning(png_ptr, "Only compression method 8 is supported by PNG");

       png_ptr->zlib_text_method = method;
    }
    #endif /* PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED */
    /* end of API added to libpng-1.5.4 */

    void PNGAPI
    png_set_write_status_fn(png_structrp png_ptr, png_write_status_ptr write_row_fn)
    {
       if (png_ptr == NULL)
          return;

       png_ptr->write_row_fn = write_row_fn;
    }

    #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
    void PNGAPI
    png_set_write_user_transform_fn(png_structrp png_ptr, png_user_transform_ptr
        write_user_transform_fn)
    {
       png_debug(1, "in png_set_write_user_transform_fn");

       if (png_ptr == NULL)
          return;

       png_ptr->transformations |= PNG_USER_TRANSFORM;
       png_ptr->write_user_transform_fn = write_user_transform_fn;
    }
    #endif

    #ifdef PNG_INFO_IMAGE_SUPPORTED
    void PNGAPI
    png_write_png(png_structrp png_ptr, png_inforp info_ptr,
        int transforms, voidp params)
    {
       if (png_ptr == NULL || info_ptr == NULL)
          return;

       /* Write the file header information. */
       png_write_info(png_ptr, info_ptr);

       /* ------ these transformations don't touch the info structure ------- */

    #ifdef PNG_WRITE_INVERT_SUPPORTED
       /* Invert monochrome pixels */
       if (transforms & PNG_TRANSFORM_INVERT_MONO)
          png_set_invert_mono(png_ptr);
    #endif

    #ifdef PNG_WRITE_SHIFT_SUPPORTED
       /* Shift the pixels up to a legal bit depth and fill in
        * as appropriate to correctly scale the image.
        */
       if ((transforms & PNG_TRANSFORM_SHIFT)
           && (info_ptr->valid & PNG_INFO_sBIT))
          png_set_shift(png_ptr, &info_ptr->sig_bit);
    #endif

    #ifdef PNG_WRITE_PACK_SUPPORTED
       /* Pack pixels into bytes */
       if (transforms & PNG_TRANSFORM_PACKING)
           png_set_packing(png_ptr);
    #endif

    #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
       /* Swap location of alpha bytes from ARGB to RGBA */
       if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
          png_set_swap_alpha(png_ptr);
    #endif

    #ifdef PNG_WRITE_FILLER_SUPPORTED
       /* Pack XRGB/RGBX/ARGB/RGBA into RGB (4 channels -> 3 channels) */
       if (transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER)
          png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);

       else if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)
          png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
    #endif

    #ifdef PNG_WRITE_BGR_SUPPORTED
       /* Flip BGR pixels to RGB */
       if (transforms & PNG_TRANSFORM_BGR)
          png_set_bgr(png_ptr);
    #endif

    #ifdef PNG_WRITE_SWAP_SUPPORTED
       /* Swap bytes of 16-bit files to most significant byte first */
       if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
          png_set_swap(png_ptr);
    #endif

    #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
       /* Swap bits of 1, 2, 4 bit packed pixel formats */
       if (transforms & PNG_TRANSFORM_PACKSWAP)
          png_set_packswap(png_ptr);
    #endif

    #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
       /* Invert the alpha channel from opacity to transparency */
       if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
          png_set_invert_alpha(png_ptr);
    #endif

       /* ----------------------- end of transformations ------------------- */

       /* Write the bits */
       if (info_ptr->valid & PNG_INFO_IDAT)
           png_write_image(png_ptr, info_ptr->row_pointers);

       /* It is REQUIRED to call this to finish writing the rest of the file */
       png_write_end(png_ptr, info_ptr);

       PNG_UNUSED(transforms)   /* Quiet compiler warnings */
       PNG_UNUSED(params)
    }
    #endif

    #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
    #ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */
    /* Initialize the write structure - general purpose utility. */
    static int
    png_image_write_init(png_imagep image)
    {
       png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, image,
              png_safe_error, png_safe_warning);

       if (png_ptr != NULL)
       {
          png_infop info_ptr = png_create_info_struct(png_ptr);

          if (info_ptr != NULL)
          {
             png_controlp control = png_voidcast(png_controlp,
                png_malloc_warn(png_ptr, (sizeof *control)));

             if (control != NULL)
             {
                memset(control, 0, (sizeof *control));

                control->png_ptr = png_ptr;
                control->info_ptr = info_ptr;
                control->for_write = 1;

                image->opaque = control;
                return 1;
             }

             /* Error clean up */
             png_destroy_info_struct(png_ptr, &info_ptr);
          }

          png_destroy_write_struct(&png_ptr, NULL);
       }

       return png_image_error(image, "png_image_write_: out of memory");
    }

    /* Arguments to png_image_write_main: */
    typedef struct
    {
       /* Arguments: */
       png_imagep      image;
       png_const_voidp buffer;
       png_int_32      row_stride;
       png_const_voidp colormap;
       int             convert_to_8bit;
       /* Local variables: */
       png_const_voidp first_row;
       ptrdiff_t       row_bytes;
       png_voidp       local_row;
    } png_image_write_control;

    /* Write png_uint_16 input to a 16-bit PNG; the png_ptr has already been set to
     * do any necessary byte swapping.  The component order is defined by the
     * png_image format value.
     */
    static int
    png_write_image_16bit(png_voidp argument)
    {
       png_image_write_control *display = png_voidcast(png_image_write_control*,
          argument);
       png_imagep image = display->image;
       png_structrp png_ptr = image->opaque->png_ptr;

       png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
          display->first_row);
       png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);
       png_uint_16p row_end;
       const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;
       int aindex = 0;
       png_uint_32 y = image->height;

       if (image->format & PNG_FORMAT_FLAG_ALPHA)
       {
          if (image->format & PNG_FORMAT_FLAG_AFIRST)
          {
             aindex = -1;
             ++input_row; /* To point to the first component */
             ++output_row;
          }

          else
             aindex = channels;
       }

       else
          png_error(png_ptr, "png_write_image: internal call error");

       /* Work out the output row end and count over this, note that the increment
        * above to 'row' means that row_end can actually be beyond the end of the
        * row; this is correct.
        */
       row_end = output_row + image->width * (channels+1);

       while (y-- > 0)
       {
          png_const_uint_16p in_ptr = input_row;
          png_uint_16p out_ptr = output_row;

          while (out_ptr < row_end)
          {
             const png_uint_16 alpha = in_ptr[aindex];
             png_uint_32 reciprocal = 0;
             int c;

             out_ptr[aindex] = alpha;

             /* Calculate a reciprocal.  The correct calculation is simply
              * component/alpha*65535 << 15. (I.e. 15 bits of precision); this
              * allows correct rounding by adding .5 before the shift.  'reciprocal'
              * is only initialized when required.
              */
             if (alpha > 0 && alpha < 65535)
                reciprocal = ((0xffff<<15)+(alpha>>1))/alpha;

             c = channels;
             do /* always at least one channel */
             {
                png_uint_16 component = *in_ptr++;

                /* The following gives 65535 for an alpha of 0, which is fine,
                 * otherwise if 0/0 is represented as some other value there is more
                 * likely to be a discontinuity which will probably damage
                 * compression when moving from a fully transparent area to a
                 * nearly transparent one.  (The assumption here is that opaque
                 * areas tend not to be 0 intensity.)
                 */
                if (component >= alpha)
                   component = 65535;

                /* component<alpha, so component/alpha is less than one and
                 * component*reciprocal is less than 2^31.
                 */
                else if (component > 0 && alpha < 65535)
                {
                   png_uint_32 calc = component * reciprocal;
                   calc += 16384; /* round to nearest */
                   component = (png_uint_16)(calc >> 15);
                }

                *out_ptr++ = component;
             }
             while (--c > 0);

             /* Skip to next component (skip the intervening alpha channel) */
             ++in_ptr;
             ++out_ptr;
          }

          png_write_row(png_ptr, png_voidcast(png_const_bytep, display->local_row));
          input_row += display->row_bytes/(sizeof (png_uint_16));
       }

       return 1;
    }

    /* Given 16-bit input (1 to 4 channels) write 8-bit output.  If an alpha channel
     * is present it must be removed from the components, the components are then
     * written in sRGB encoding.  No components are added or removed.
     *
     * Calculate an alpha reciprocal to reverse pre-multiplication.  As above the
     * calculation can be done to 15 bits of accuracy; however, the output needs to
     * be scaled in the range 0..255*65535, so include that scaling here.
     */
    #define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)

    static png_byte
    png_unpremultiply(png_uint_32 component, png_uint_32 alpha,
       png_uint_32 reciprocal/*from the above macro*/)
    {
       /* The following gives 1.0 for an alpha of 0, which is fine, otherwise if 0/0
        * is represented as some other value there is more likely to be a
        * discontinuity which will probably damage compression when moving from a
        * fully transparent area to a nearly transparent one.  (The assumption here
        * is that opaque areas tend not to be 0 intensity.)
        *
        * There is a rounding problem here; if alpha is less than 128 it will end up
        * as 0 when scaled to 8 bits.  To avoid introducing spurious colors into the
        * output change for this too.
        */
       if (component >= alpha || alpha < 128)
          return 255;

       /* component<alpha, so component/alpha is less than one and
        * component*reciprocal is less than 2^31.
        */
       else if (component > 0)
       {
          /* The test is that alpha/257 (rounded) is less than 255, the first value
           * that becomes 255 is 65407.
           * NOTE: this must agree with the PNG_DIV257 macro (which must, therefore,
           * be exact!)  [Could also test reciprocal != 0]
           */
          if (alpha < 65407)
          {
             component *= reciprocal;
             component += 64; /* round to nearest */
             component >>= 7;
          }

          else
             component *= 255;

          /* Convert the component to sRGB. */
          return (png_byte)PNG_sRGB_FROM_LINEAR(component);
       }

       else
          return 0;
    }

    static int
    png_write_image_8bit(png_voidp argument)
    {
       png_image_write_control *display = png_voidcast(png_image_write_control*,
          argument);
       png_imagep image = display->image;
       png_structrp png_ptr = image->opaque->png_ptr;

       png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,
          display->first_row);
       png_bytep output_row = png_voidcast(png_bytep, display->local_row);
       png_uint_32 y = image->height;
       const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;

       if (image->format & PNG_FORMAT_FLAG_ALPHA)
       {
          png_bytep row_end;
          int aindex;

          if (image->format & PNG_FORMAT_FLAG_AFIRST)
          {
             aindex = -1;
             ++input_row; /* To point to the first component */
             ++output_row;
          }

          else
             aindex = channels;

          /* Use row_end in place of a loop counter: */
          row_end = output_row + image->width * (channels+1);

          while (y-- > 0)
          {
             png_const_uint_16p in_ptr = input_row;
             png_bytep out_ptr = output_row;

             while (out_ptr < row_end)
             {
                png_uint_16 alpha = in_ptr[aindex];
                png_byte alphabyte = (png_byte)PNG_DIV257(alpha);
                png_uint_32 reciprocal = 0;
                int c;

                /* Scale and write the alpha channel. */
                out_ptr[aindex] = alphabyte;

                if (alphabyte > 0 && alphabyte < 255)
                   reciprocal = UNP_RECIPROCAL(alpha);

                c = channels;
                do /* always at least one channel */
                   *out_ptr++ = png_unpremultiply(*in_ptr++, alpha, reciprocal);
                while (--c > 0);

                /* Skip to next component (skip the intervening alpha channel) */
                ++in_ptr;
                ++out_ptr;
             } /* while out_ptr < row_end */

             png_write_row(png_ptr, png_voidcast(png_const_bytep,
                display->local_row));
             input_row += display->row_bytes/(sizeof (png_uint_16));
          } /* while y */
       }

       else
       {
          /* No alpha channel, so the row_end really is the end of the row and it
           * is sufficient to loop over the components one by one.
           */
          png_bytep row_end = output_row + image->width * channels;

          while (y-- > 0)
          {
             png_const_uint_16p in_ptr = input_row;
             png_bytep out_ptr = output_row;

             while (out_ptr < row_end)
             {
                png_uint_32 component = *in_ptr++;

                component *= 255;
                *out_ptr++ = (png_byte)PNG_sRGB_FROM_LINEAR(component);
             }

             png_write_row(png_ptr, output_row);
             input_row += display->row_bytes/(sizeof (png_uint_16));
          }
       }

       return 1;
    }

    static void
    png_image_set_PLTE(png_image_write_control *display)
    {
       const png_imagep image = display->image;
       const void *cmap = display->colormap;
       const int entries = image->colormap_entries > 256 ? 256 :
          (int)image->colormap_entries;

       /* NOTE: the caller must check for cmap != NULL and entries != 0 */
       const png_uint_32 format = image->format;
       const int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);

    #  ifdef PNG_FORMAT_BGR_SUPPORTED
          const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
             (format & PNG_FORMAT_FLAG_ALPHA) != 0;
    #  else
    #     define afirst 0
    #  endif

    #  ifdef PNG_FORMAT_BGR_SUPPORTED
          const int bgr = (format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;
    #  else
    #     define bgr 0
    #  endif

       int i, num_trans;
       png_color palette[256];
       png_byte tRNS[256];

       memset(tRNS, 255, (sizeof tRNS));
       memset(palette, 0, (sizeof palette));

       for (i=num_trans=0; i<entries; ++i)
       {
          /* This gets automatically converted to sRGB with reversal of the
           * pre-multiplication if the color-map has an alpha channel.
           */
          if (format & PNG_FORMAT_FLAG_LINEAR)
          {
             png_const_uint_16p entry = png_voidcast(png_const_uint_16p, cmap);

             entry += i * channels;

             if (channels & 1) /* no alpha */
             {
                if (channels >= 3) /* RGB */
                {
                   palette[i].blue = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
                      entry[(2 ^ bgr)]);
                   palette[i].green = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
                      entry[1]);
                   palette[i].red = (png_byte)PNG_sRGB_FROM_LINEAR(255 *
                      entry[bgr]);
                }

                else /* Gray */
                   palette[i].blue = palette[i].red = palette[i].green =
                      (png_byte)PNG_sRGB_FROM_LINEAR(255 * *entry);
             }

             else /* alpha */
             {
                png_uint_16 alpha = entry[afirst ? 0 : channels-1];
                png_byte alphabyte = (png_byte)PNG_DIV257(alpha);
                png_uint_32 reciprocal = 0;

                /* Calculate a reciprocal, as in the png_write_image_8bit code above
                 * this is designed to produce a value scaled to 255*65535 when
                 * divided by 128 (i.e. asr 7).
                 */
                if (alphabyte > 0 && alphabyte < 255)
                   reciprocal = (((0xffff*0xff)<<7)+(alpha>>1))/alpha;

                tRNS[i] = alphabyte;
                if (alphabyte < 255)
                   num_trans = i+1;

                if (channels >= 3) /* RGB */
                {
                   palette[i].blue = png_unpremultiply(entry[afirst + (2 ^ bgr)],
                      alpha, reciprocal);
                   palette[i].green = png_unpremultiply(entry[afirst + 1], alpha,
                      reciprocal);
                   palette[i].red = png_unpremultiply(entry[afirst + bgr], alpha,
                      reciprocal);
                }

                else /* gray */
                   palette[i].blue = palette[i].red = palette[i].green =
                      png_unpremultiply(entry[afirst], alpha, reciprocal);
             }
          }

          else /* Color-map has sRGB values */
          {
             png_const_bytep entry = png_voidcast(png_const_bytep, cmap);

             entry += i * channels;

             switch (channels)
             {
                case 4:
                   tRNS[i] = entry[afirst ? 0 : 3];
                   if (tRNS[i] < 255)
                      num_trans = i+1;
                   /* FALL THROUGH */
                case 3:
                   palette[i].blue = entry[afirst + (2 ^ bgr)];
                   palette[i].green = entry[afirst + 1];
                   palette[i].red = entry[afirst + bgr];
                   break;

                case 2:
                   tRNS[i] = entry[1 ^ afirst];
                   if (tRNS[i] < 255)
                      num_trans = i+1;
                   /* FALL THROUGH */
                case 1:
                   palette[i].blue = palette[i].red = palette[i].green =
                      entry[afirst];
                   break;

                default:
                   break;
             }
          }
       }

    #  ifdef afirst
    #     undef afirst
    #  endif
    #  ifdef bgr
    #     undef bgr
    #  endif

       png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,
          entries);

       if (num_trans > 0)
          png_set_tRNS(image->opaque->png_ptr, image->opaque->info_ptr, tRNS,
             num_trans, NULL);

       image->colormap_entries = entries;
    }

    static int
    png_image_write_main(png_voidp argument)
    {
       png_image_write_control *display = png_voidcast(png_image_write_control*,
          argument);
       png_imagep image = display->image;
       png_structrp png_ptr = image->opaque->png_ptr;
       png_inforp info_ptr = image->opaque->info_ptr;
       png_uint_32 format = image->format;

       int colormap = (format & PNG_FORMAT_FLAG_COLORMAP) != 0;
       int linear = !colormap && (format & PNG_FORMAT_FLAG_LINEAR) != 0; /* input */
       int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0;
       int write_16bit = linear && !colormap && !display->convert_to_8bit;

    #  ifdef PNG_BENIGN_ERRORS_SUPPORTED
          /* Make sure we error out on any bad situation */
          png_set_benign_errors(png_ptr, 0/*error*/);
    #  endif

       /* Default the 'row_stride' parameter if required. */
       if (display->row_stride == 0)
          display->row_stride = PNG_IMAGE_ROW_STRIDE(*image);

       /* Set the required transforms then write the rows in the correct order. */
       if (format & PNG_FORMAT_FLAG_COLORMAP)
       {
          if (display->colormap != NULL && image->colormap_entries > 0)
          {
             png_uint_32 entries = image->colormap_entries;

             png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
                entries > 16 ? 8 : (entries > 4 ? 4 : (entries > 2 ? 2 : 1)),
                PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,
                PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

             png_image_set_PLTE(display);
          }

          else
             png_error(image->opaque->png_ptr,
                "no color-map for color-mapped image");
       }

       else
          png_set_IHDR(png_ptr, info_ptr, image->width, image->height,
             write_16bit ? 16 : 8,
             ((format & PNG_FORMAT_FLAG_COLOR) ? PNG_COLOR_MASK_COLOR : 0) +
             ((format & PNG_FORMAT_FLAG_ALPHA) ? PNG_COLOR_MASK_ALPHA : 0),
             PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

       /* Counter-intuitively the data transformations must be called *after*
        * png_write_info, not before as in the read code, but the 'set' functions
        * must still be called before.  Just set the color space information, never
        * write an interlaced image.
        */

       if (write_16bit)
       {
          /* The gamma here is 1.0 (linear) and the cHRM chunk matches sRGB. */
          png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_LINEAR);

          if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))
             png_set_cHRM_fixed(png_ptr, info_ptr,
                /* color      x       y */
                /* white */ 31270, 32900,
                /* red   */ 64000, 33000,
                /* green */ 30000, 60000,
                /* blue  */ 15000,  6000
             );
       }

       else if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))
          png_set_sRGB(png_ptr, info_ptr, PNG_sRGB_INTENT_PERCEPTUAL);

       /* Else writing an 8-bit file and the *colors* aren't sRGB, but the 8-bit
        * space must still be gamma encoded.
        */
       else
          png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_sRGB_INVERSE);

       /* Write the file header. */
       png_write_info(png_ptr, info_ptr);

       /* Now set up the data transformations (*after* the header is written),
        * remove the handled transformations from the 'format' flags for checking.
        *
        * First check for a little endian system if writing 16 bit files.
        */
       if (write_16bit)
       {
          PNG_CONST png_uint_16 le = 0x0001;

          if (*(png_const_bytep)&le)
             png_set_swap(png_ptr);
       }

    #  ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
          if (format & PNG_FORMAT_FLAG_BGR)
          {
             if (!colormap && (format & PNG_FORMAT_FLAG_COLOR) != 0)
                png_set_bgr(png_ptr);
             format &= ~PNG_FORMAT_FLAG_BGR;
          }
    #  endif

    #  ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
          if (format & PNG_FORMAT_FLAG_AFIRST)
          {
             if (!colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0)
                png_set_swap_alpha(png_ptr);
             format &= ~PNG_FORMAT_FLAG_AFIRST;
          }
    #  endif

       /* If there are 16 or fewer color-map entries we wrote a lower bit depth
        * above, but the application data is still byte packed.
        */
       if (colormap && image->colormap_entries <= 16)
          png_set_packing(png_ptr);

       /* That should have handled all (both) the transforms. */
       if ((format & ~(png_uint_32)(PNG_FORMAT_FLAG_COLOR | PNG_FORMAT_FLAG_LINEAR |
             PNG_FORMAT_FLAG_ALPHA | PNG_FORMAT_FLAG_COLORMAP)) != 0)
          png_error(png_ptr, "png_write_image: unsupported transformation");

       {
          png_const_bytep row = png_voidcast(png_const_bytep, display->buffer);
          ptrdiff_t row_bytes = display->row_stride;

          if (linear)
             row_bytes *= (sizeof (png_uint_16));

          if (row_bytes < 0)
             row += (image->height-1) * (-row_bytes);

          display->first_row = row;
          display->row_bytes = row_bytes;
       }

       /* Apply 'fast' options if the flag is set. */
       if ((image->flags & PNG_IMAGE_FLAG_FAST) != 0)
       {
          png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);
          /* NOTE: determined by experiment using pngstest, this reflects some
           * balance between the time to write the image once and the time to read
           * it about 50 times.  The speed-up in pngstest was about 10-20% of the
           * total (user) time on a heavily loaded system.
           */
          png_set_compression_level(png_ptr, 3);
       }

       /* Check for the cases that currently require a pre-transform on the row
        * before it is written.  This only applies when the input is 16-bit and
        * either there is an alpha channel or it is converted to 8-bit.
        */
       if ((linear && alpha) || (!colormap && display->convert_to_8bit))
       {
          png_bytep row = png_voidcast(png_bytep, png_malloc(png_ptr,
             png_get_rowbytes(png_ptr, info_ptr)));
          int result;

          display->local_row = row;
          if (write_16bit)
             result = png_safe_execute(image, png_write_image_16bit, display);
          else
             result = png_safe_execute(image, png_write_image_8bit, display);
          display->local_row = NULL;

          png_free(png_ptr, row);

          /* Skip the 'write_end' on error: */
          if (!result)
             return 0;
       }

       /* Otherwise this is the case where the input is in a format currently
        * supported by the rest of the libpng write code; call it directly.
        */
       else
       {
          png_const_bytep row = png_voidcast(png_const_bytep, display->first_row);
          ptrdiff_t row_bytes = display->row_bytes;
          png_uint_32 y = image->height;

          while (y-- > 0)
          {
             png_write_row(png_ptr, row);
             row += row_bytes;
          }
       }

       png_write_end(png_ptr, info_ptr);
       return 1;
    }

    int PNGAPI
    png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,
       const void *buffer, png_int_32 row_stride, const void *colormap)
    {
       /* Write the image to the given (FILE*). */
       if (image != NULL && image->version == PNG_IMAGE_VERSION)
       {
          if (file != NULL)
          {
             if (png_image_write_init(image))
             {
                png_image_write_control display;
                int result;

                /* This is slightly evil, but png_init_io doesn't do anything other
                 * than this and we haven't changed the standard IO functions so
                 * this saves a 'safe' function.
                 */
                image->opaque->png_ptr->io_ptr = file;

                memset(&display, 0, (sizeof display));
                display.image = image;
                display.buffer = buffer;
                display.row_stride = row_stride;
                display.colormap = colormap;
                display.convert_to_8bit = convert_to_8bit;

                result = png_safe_execute(image, png_image_write_main, &display);
                png_image_free(image);
                return result;
             }

             else
                return 0;
          }

          else
             return png_image_error(image,
                "png_image_write_to_stdio: invalid argument");
       }

       else if (image != NULL)
          return png_image_error(image,
             "png_image_write_to_stdio: incorrect PNG_IMAGE_VERSION");

       else
          return 0;
    }

    int PNGAPI
    png_image_write_to_file(png_imagep image, const char *file_name,
       int convert_to_8bit, const void *buffer, png_int_32 row_stride,
       const void *colormap)
    {
       /* Write the image to the named file. */
       if (image != NULL && image->version == PNG_IMAGE_VERSION)
       {
          if (file_name != NULL)
          {
             FILE *fp = fopen(file_name, "wb");

             if (fp != NULL)
             {
                if (png_image_write_to_stdio(image, fp, convert_to_8bit, buffer,
                   row_stride, colormap))
                {
                   int error; /* from fflush/fclose */

                   /* Make sure the file is flushed correctly. */
                   if (fflush(fp) == 0 && ferror(fp) == 0)
                   {
                      if (fclose(fp) == 0)
                         return 1;

                      error = errno; /* from fclose */
                   }

                   else
                   {
                      error = errno; /* from fflush or ferror */
                      (void)fclose(fp);
                   }

                   (void)remove(file_name);
                   /* The image has already been cleaned up; this is just used to
                    * set the error (because the original write succeeded).
                    */
                   return png_image_error(image, strerror(error));
                }

                else
                {
                   /* Clean up: just the opened file. */
                   (void)fclose(fp);
                   (void)remove(file_name);
                   return 0;
                }
             }

             else
                return png_image_error(image, strerror(errno));
          }

          else
             return png_image_error(image,
                "png_image_write_to_file: invalid argument");
       }

       else if (image != NULL)
          return png_image_error(image,
             "png_image_write_to_file: incorrect PNG_IMAGE_VERSION");

       else
          return 0;
    }
    #endif /* PNG_STDIO_SUPPORTED */
    #endif /* SIMPLIFIED_WRITE */
    #endif /* PNG_WRITE_SUPPORTED */