tor-browser

pngwrite.c (80181B)

---

/* pngwrite.c - general routines to write a PNG file
*
* Copyright (c) 2018-2025 Cosmin Truta
* Copyright (c) 1998-2002,2004,2006-2018 Glenn Randers-Pehrson
* Copyright (c) 1996-1997 Andreas Dilger
* 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"
#ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
#  include <errno.h>
#endif /* SIMPLIFIED_WRITE_STDIO */

#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 != 0)
  {
     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) != 0)
     {
        /* 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 /* WRITE_UNKNOWN_CHUNKS */

/* 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_<chunk> 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) == 0)
  {
     /* Write PNG signature */
     png_write_sig(png_ptr);

#ifdef PNG_MNG_FEATURES_SUPPORTED
     if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \
         png_ptr->mng_features_permitted != 0)
     {
        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
      * an 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_WRITE_APNG_SUPPORTED
  if ((info_ptr->valid & PNG_INFO_acTL) != 0)
     png_write_acTL(png_ptr, info_ptr->num_frames, info_ptr->num_plays);
#endif
#ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
        /* Write unknown chunks first; PNG v3 establishes a precedence order
         * for colourspace chunks.  It is certain therefore that new
         * colourspace chunks will have a precedence and very likely it will be
         * higher than all known so far.  Writing the unknown chunks here is
         * most likely to present the chunks in the most convenient order.
         *
         * FUTURE: maybe write chunks in the order the app calls png_set_chnk
         * to give the app control.
         */
        write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);
#endif

#ifdef PNG_WRITE_sBIT_SUPPORTED
        /* PNG v3: a streaming app will need to see this before cICP because
         * the information is helpful in handling HLG encoding (which is
         * natively 10 bits but gets expanded to 16 in PNG.)
         *
         * The app shouldn't care about the order ideally, but it might have
         * no choice.  In PNG v3, apps are allowed to reject PNGs where the
         * APNG chunks are out of order so it behooves libpng to be nice here.
         */
        if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
           png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
#endif

  /* PNG v3: the July 2004 version of the TR introduced the concept of colour
   * space priority.  As above it therefore behooves libpng to write the colour
   * space chunks in the priority order so that a streaming app need not buffer
   * them.
   *
   * PNG v3: Chunks mDCV and cLLI provide ancillary information for the
   * interpretation of the colourspace chunkgs but do not require support for
   * those chunks so are outside the "COLORSPACE" check but before the write of
   * the colourspace chunks themselves.
   */
#ifdef PNG_WRITE_cLLI_SUPPORTED
  if ((info_ptr->valid & PNG_INFO_cLLI) != 0)
  {
     png_write_cLLI_fixed(png_ptr, info_ptr->maxCLL, info_ptr->maxFALL);
  }
#endif
#ifdef PNG_WRITE_mDCV_SUPPORTED
  if ((info_ptr->valid & PNG_INFO_mDCV) != 0)
  {
     png_write_mDCV_fixed(png_ptr,
        info_ptr->mastering_red_x, info_ptr->mastering_red_y,
        info_ptr->mastering_green_x, info_ptr->mastering_green_y,
        info_ptr->mastering_blue_x, info_ptr->mastering_blue_y,
        info_ptr->mastering_white_x, info_ptr->mastering_white_y,
        info_ptr->mastering_maxDL, info_ptr->mastering_minDL);
  }
#endif

#  ifdef PNG_WRITE_cICP_SUPPORTED /* Priority 4 */
  if ((info_ptr->valid & PNG_INFO_cICP) != 0)
     {
        png_write_cICP(png_ptr,
                       info_ptr->cicp_colour_primaries,
                       info_ptr->cicp_transfer_function,
                       info_ptr->cicp_matrix_coefficients,
                       info_ptr->cicp_video_full_range_flag);
     }
#  endif

#  ifdef PNG_WRITE_iCCP_SUPPORTED /* Priority 3 */
        if ((info_ptr->valid & PNG_INFO_iCCP) != 0)
        {
           png_write_iCCP(png_ptr, info_ptr->iccp_name,
               info_ptr->iccp_profile, info_ptr->iccp_proflen);
        }
#  endif

#  ifdef PNG_WRITE_sRGB_SUPPORTED /* Priority 2 */
        if ((info_ptr->valid & PNG_INFO_sRGB) != 0)
           png_write_sRGB(png_ptr, info_ptr->rendering_intent);
#  endif /* WRITE_sRGB */

#  ifdef PNG_WRITE_gAMA_SUPPORTED /* Priority 1 */
     if ((info_ptr->valid & PNG_INFO_gAMA) != 0)
        png_write_gAMA_fixed(png_ptr, info_ptr->gamma);
#  endif

#  ifdef PNG_WRITE_cHRM_SUPPORTED /* Also priority 1 */
        if ((info_ptr->valid & PNG_INFO_cHRM) != 0)
           png_write_cHRM_fixed(png_ptr, &info_ptr->cHRM);
#  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) != 0)
     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) !=0)
  {
#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
     /* Invert the alpha channel (in tRNS) */
     if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&
         info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
     {
        int j, jend;

        jend = info_ptr->num_trans;
        if (jend > PNG_MAX_PALETTE_LENGTH)
           jend = PNG_MAX_PALETTE_LENGTH;

        for (j = 0; j<jend; ++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) != 0)
     png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
#endif

#ifdef PNG_WRITE_eXIf_SUPPORTED
  if ((info_ptr->valid & PNG_INFO_eXIf) != 0)
  {
     png_write_eXIf(png_ptr, info_ptr->exif, info_ptr->num_exif);
     png_ptr->mode |= PNG_WROTE_eXIf;
  }
#endif

#ifdef PNG_WRITE_hIST_SUPPORTED
  if ((info_ptr->valid & PNG_INFO_hIST) != 0)
     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) != 0)
     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) != 0)
     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) != 0)
     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) != 0)
     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) != 0)
  {
     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) != 0)
     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);
        /* Mark this chunk as written */
        if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
           info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
        else
           info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
        png_warning(png_ptr, "Unable to write international text");
#endif
     }

     /* 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, info_ptr->text[i].compression);
        /* Mark this chunk as written */
        info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
        png_warning(png_ptr, "Unable to write compressed text");
#endif
     }

     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) == 0)
     png_error(png_ptr, "No IDATs written into file");

#ifdef PNG_WRITE_APNG_SUPPORTED
  if (png_ptr->num_frames_written != png_ptr->num_frames_to_write)
     png_error(png_ptr, "Not enough frames written");
#endif

#ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED
  if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
      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) != 0 &&
         (png_ptr->mode & PNG_WROTE_tIME) == 0)
        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);
           /* Mark this chunk as written */
           if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
              info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
           else
              info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
           png_warning(png_ptr, "Unable to write international text");
#endif
        }

        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, info_ptr->text[i].compression);
           /* Mark this chunk as written */
           info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
#else
           png_warning(png_ptr, "Unable to write compressed text");
#endif
        }

        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
           png_warning(png_ptr, "Unable to write uncompressed text");
#endif
        }
     }
#endif

#ifdef PNG_WRITE_eXIf_SUPPORTED
     if ((info_ptr->valid & PNG_INFO_eXIf) != 0 &&
         (png_ptr->mode & PNG_WROTE_eXIf) == 0)
        png_write_eXIf(png_ptr, info_ptr->exif, info_ptr->num_exif);
#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, 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);
  if (tbuf == NULL)
  {
     /* TODO: add a safe function which takes a png_ptr argument and raises
      * a png_error if the ttime argument is invalid and the call to gmtime
      * fails as a consequence.
      */
     memset(ptime, 0, sizeof(*ptime));
     return;
  }

  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 /* USER_MEM */
  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 /* WRITE_COMPRESSED_TEXT */

     /* 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
     /* In stable builds only warn if an application error can be completely
      * handled.
      */
     png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;
#endif

     /* App warnings are warnings in release (or release candidate) builds but
      * are errors during development.
      */
#if PNG_RELEASE_BUILD
     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);
     }
  }
}

#ifdef PNG_MNG_FEATURES_SUPPORTED
/* Performs intrapixel differencing  */
static void
png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
{
  png_debug(1, "in png_do_write_intrapixel");

  if ((row_info->color_type & PNG_COLOR_MASK_COLOR) != 0)
  {
     int bytes_per_pixel;
     png_uint_32 row_width = row_info->width;
     if (row_info->bit_depth == 8)
     {
        png_bytep rp;
        png_uint_32 i;

        if (row_info->color_type == PNG_COLOR_TYPE_RGB)
           bytes_per_pixel = 3;

        else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
           bytes_per_pixel = 4;

        else
           return;

        for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
        {
           *(rp)     = (png_byte)(*rp       - *(rp + 1));
           *(rp + 2) = (png_byte)(*(rp + 2) - *(rp + 1));
        }
     }

#ifdef PNG_WRITE_16BIT_SUPPORTED
     else if (row_info->bit_depth == 16)
     {
        png_bytep rp;
        png_uint_32 i;

        if (row_info->color_type == PNG_COLOR_TYPE_RGB)
           bytes_per_pixel = 6;

        else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
           bytes_per_pixel = 8;

        else
           return;

        for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
        {
           png_uint_32 s0   = (png_uint_32)(*(rp    ) << 8) | *(rp + 1);
           png_uint_32 s1   = (png_uint_32)(*(rp + 2) << 8) | *(rp + 3);
           png_uint_32 s2   = (png_uint_32)(*(rp + 4) << 8) | *(rp + 5);
           png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
           png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
           *(rp    ) = (png_byte)(red >> 8);
           *(rp + 1) = (png_byte)red;
           *(rp + 4) = (png_byte)(blue >> 8);
           *(rp + 5) = (png_byte)blue;
        }
     }
#endif /* WRITE_16BIT */
  }
}
#endif /* MNG_FEATURES */

/* 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;

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

  if (png_ptr == NULL)
     return;

  /* 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) == 0)
        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) != 0)
        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) != 0)
        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) != 0)
        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) != 0)
        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) != 0)
        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) != 0)
        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) != 0)
        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 != 0 &&
      (png_ptr->transformations & PNG_INTERLACE) != 0)
  {
     switch (png_ptr->pass)
     {
        case 0:
           if ((png_ptr->row_number & 0x07) != 0)
           {
              png_write_finish_row(png_ptr);
              return;
           }
           break;

        case 1:
           if ((png_ptr->row_number & 0x07) != 0 || 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) != 0 || 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) != 0 || png_ptr->width < 2)
           {
              png_write_finish_row(png_ptr);
              return;
           }
           break;

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

#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
  /* Handle other transformations */
  if (png_ptr->transformations != 0)
     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) != 0 &&
      (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 : (png_uint_32)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 /* WRITE_FLUSH */

/* 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) != 0)
     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);
  png_ptr->row_buf = NULL;
#ifdef PNG_WRITE_FILTER_SUPPORTED
  png_free(png_ptr, png_ptr->prev_row);
  png_free(png_ptr, png_ptr->try_row);
  png_free(png_ptr, png_ptr->tst_row);
  png_ptr->prev_row = NULL;
  png_ptr->try_row = NULL;
  png_ptr->tst_row = NULL;
#endif

#ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED
  png_free(png_ptr, png_ptr->chunk_list);
  png_ptr->chunk_list = NULL;
#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) != 0 &&
      (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");
#endif /* WRITE_FILTER */
           /* FALLTHROUGH */
        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 /* WRITE_FILTER */
     }

#ifdef 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 remove them
      * or add them back after the start of compression.
      *
      * NOTE: this is a nasty constraint on the code, because it means that the
      * prev_row buffer must be maintained even if there are currently no
      * 'prev_row' requiring filters active.
      */
     if (png_ptr->row_buf != NULL)
     {
        int num_filters;
        png_alloc_size_t buf_size;

        /* Repeat the checks in png_write_start_row; 1 pixel high or wide
         * images cannot benefit from certain filters.  If this isn't done here
         * the check below will fire on 1 pixel high images.
         */
        if (png_ptr->height == 1)
           filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);

        if (png_ptr->width == 1)
           filters &= ~(PNG_FILTER_SUB|PNG_FILTER_AVG|PNG_FILTER_PAETH);

        if ((filters & (PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH)) != 0
           && png_ptr->prev_row == NULL)
        {
           /* This is the error case, however it is benign - the previous row
            * is not available so the filter can't be used.  Just warn here.
            */
           png_app_warning(png_ptr,
               "png_set_filter: UP/AVG/PAETH cannot be added after start");
           filters &= ~(PNG_FILTER_UP|PNG_FILTER_AVG|PNG_FILTER_PAETH);
        }

        num_filters = 0;

        if (filters & PNG_FILTER_SUB)
           num_filters++;

        if (filters & PNG_FILTER_UP)
           num_filters++;

        if (filters & PNG_FILTER_AVG)
           num_filters++;

        if (filters & PNG_FILTER_PAETH)
           num_filters++;

        /* Allocate needed row buffers if they have not already been
         * allocated.
         */
        buf_size = PNG_ROWBYTES(png_ptr->usr_channels * png_ptr->usr_bit_depth,
            png_ptr->width) + 1;

        if (png_ptr->try_row == NULL)
           png_ptr->try_row = png_voidcast(png_bytep,
               png_malloc(png_ptr, buf_size));

        if (num_filters > 1)
        {
           if (png_ptr->tst_row == NULL)
              png_ptr->tst_row = png_voidcast(png_bytep,
                  png_malloc(png_ptr, buf_size));
        }
     }
     png_ptr->do_filter = (png_byte)filters;
#endif
  }
  else
     png_error(png_ptr, "Unknown custom filter method");
}

#ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED /* DEPRECATED */
/* 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_UNUSED(png_ptr)
  PNG_UNUSED(heuristic_method)
  PNG_UNUSED(num_weights)
  PNG_UNUSED(filter_weights)
  PNG_UNUSED(filter_costs)
}
#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_UNUSED(png_ptr)
  PNG_UNUSED(heuristic_method)
  PNG_UNUSED(num_weights)
  PNG_UNUSED(filter_weights)
  PNG_UNUSED(filter_costs)
}
#endif /* FIXED_POINT */
#endif /* WRITE_WEIGHTED_FILTER */

#ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_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)
{
  png_debug(1, "in png_set_compression_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 that 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;
}
#endif /* WRITE_CUSTOMIZE_COMPRESSION */

/* 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)
{
  png_debug(1, "in png_set_text_compression_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 /* WRITE_CUSTOMIZE_ZTXT_COMPRESSION */
/* 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)
{
  png_debug(1, "in png_set_write_status_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)
{
  png_debug(1, "in png_write_png");

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

  if ((info_ptr->valid & PNG_INFO_IDAT) == 0)
  {
     png_app_error(png_ptr, "no rows for png_write_image to write");
     return;
  }

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

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

  /* Invert monochrome pixels */
  if ((transforms & PNG_TRANSFORM_INVERT_MONO) != 0)
#ifdef PNG_WRITE_INVERT_SUPPORTED
     png_set_invert_mono(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");
#endif

  /* Shift the pixels up to a legal bit depth and fill in
   * as appropriate to correctly scale the image.
   */
  if ((transforms & PNG_TRANSFORM_SHIFT) != 0)
#ifdef PNG_WRITE_SHIFT_SUPPORTED
     if ((info_ptr->valid & PNG_INFO_sBIT) != 0)
        png_set_shift(png_ptr, &info_ptr->sig_bit);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");
#endif

  /* Pack pixels into bytes */
  if ((transforms & PNG_TRANSFORM_PACKING) != 0)
#ifdef PNG_WRITE_PACK_SUPPORTED
     png_set_packing(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");
#endif

  /* Swap location of alpha bytes from ARGB to RGBA */
  if ((transforms & PNG_TRANSFORM_SWAP_ALPHA) != 0)
#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
     png_set_swap_alpha(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");
#endif

  /* Remove a filler (X) from XRGB/RGBX/AG/GA into to convert it into
   * RGB, note that the code expects the input color type to be G or RGB; no
   * alpha channel.
   */
  if ((transforms & (PNG_TRANSFORM_STRIP_FILLER_AFTER|
      PNG_TRANSFORM_STRIP_FILLER_BEFORE)) != 0)
  {
#ifdef PNG_WRITE_FILLER_SUPPORTED
     if ((transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER) != 0)
     {
        if ((transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE) != 0)
           png_app_error(png_ptr,
               "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");

        /* Continue if ignored - this is the pre-1.6.10 behavior */
        png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
     }

     else if ((transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE) != 0)
        png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_FILLER not supported");
#endif
  }

  /* Flip BGR pixels to RGB */
  if ((transforms & PNG_TRANSFORM_BGR) != 0)
#ifdef PNG_WRITE_BGR_SUPPORTED
     png_set_bgr(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");
#endif

  /* Swap bytes of 16-bit files to most significant byte first */
  if ((transforms & PNG_TRANSFORM_SWAP_ENDIAN) != 0)
#ifdef PNG_WRITE_SWAP_SUPPORTED
     png_set_swap(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");
#endif

  /* Swap bits of 1-bit, 2-bit, 4-bit packed pixel formats */
  if ((transforms & PNG_TRANSFORM_PACKSWAP) != 0)
#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
     png_set_packswap(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");
#endif

  /* Invert the alpha channel from opacity to transparency */
  if ((transforms & PNG_TRANSFORM_INVERT_ALPHA) != 0)
#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
     png_set_invert_alpha(png_ptr);
#else
     png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");
#endif

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

  /* Write the bits */
  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(params)
}
#endif


#ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED
/* 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;
  /* Byte count for memory writing */
  png_bytep        memory;
  png_alloc_size_t memory_bytes; /* not used for STDIO */
  png_alloc_size_t output_bytes; /* running total */
} 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;
  unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
      3 : 1;
  int aindex = 0;
  png_uint_32 y = image->height;

  if ((image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
  {
#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
     if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
     {
        aindex = -1;
        ++input_row; /* To point to the first component */
        ++output_row;
     }
        else
           aindex = (int)channels;
#     else
        aindex = (int)channels;
#     endif
  }

  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);

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

     while (out_ptr < row_end)
     {
        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 = (int)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 += (png_uint_16)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;
  unsigned int channels = (image->format & PNG_FORMAT_FLAG_COLOR) != 0 ?
      3 : 1;

  if ((image->format & PNG_FORMAT_FLAG_ALPHA) != 0)
  {
     png_bytep row_end;
     int aindex;

#   ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED
     if ((image->format & PNG_FORMAT_FLAG_AFIRST) != 0)
     {
        aindex = -1;
        ++input_row; /* To point to the first component */
        ++output_row;
     }

     else
#   endif
     aindex = (int)channels;

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

     for (; y > 0; --y)
     {
        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 = (int)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 += (png_uint_16)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;

     for (; y > 0; --y)
     {
        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 += (png_uint_16)display->row_bytes/(sizeof (png_uint_16));
     }
  }

  return 1;
}

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

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

#   if defined(PNG_FORMAT_BGR_SUPPORTED) &&\
     defined(PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED)
     int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&
         (format & PNG_FORMAT_FLAG_ALPHA) != 0;
#   else
#     define afirst 0
#   endif

#   ifdef PNG_FORMAT_BGR_SUPPORTED
     int bgr = (format & PNG_FORMAT_FLAG_BGR) != 0 ? 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) != 0)
     {
        png_const_uint_16p entry = png_voidcast(png_const_uint_16p, cmap);

        entry += (unsigned int)i * channels;

        if ((channels & 1) != 0) /* 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 += (unsigned int)i * channels;

        switch (channels)
        {
           case 4:
              tRNS[i] = entry[afirst ? 0 : 3];
              if (tRNS[i] < 255)
                 num_trans = i+1;
              /* FALLTHROUGH */
           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;
              /* FALLTHROUGH */
           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 = (png_uint_32)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;

  /* The following four ints are actually booleans */
  int colormap = (format & PNG_FORMAT_FLAG_COLORMAP);
  int linear = !colormap && (format & PNG_FORMAT_FLAG_LINEAR); /* input */
  int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA);
  int write_16bit = linear && (display->convert_to_8bit == 0);

#   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, also check the row stride
   * and total image size to ensure that they are within the system limits.
   */
  {
     unsigned int channels = PNG_IMAGE_PIXEL_CHANNELS(image->format);

     if (image->width <= 0x7fffffffU/channels) /* no overflow */
     {
        png_uint_32 check;
        png_uint_32 png_row_stride = image->width * channels;

        if (display->row_stride == 0)
           display->row_stride = (png_int_32)/*SAFE*/png_row_stride;

        if (display->row_stride < 0)
           check = (png_uint_32)(-display->row_stride);

        else
           check = (png_uint_32)display->row_stride;

        if (check >= png_row_stride)
        {
           /* Now check for overflow of the image buffer calculation; this
            * limits the whole image size to 32 bits for API compatibility with
            * the current, 32-bit, PNG_IMAGE_BUFFER_SIZE macro.
            */
           if (image->height > 0xffffffffU/png_row_stride)
              png_error(image->opaque->png_ptr, "memory image too large");
        }

        else
           png_error(image->opaque->png_ptr, "supplied row stride too small");
     }

     else
        png_error(image->opaque->png_ptr, "image row stride too large");
  }

  /* Set the required transforms then write the rows in the correct order. */
  if ((format & PNG_FORMAT_FLAG_COLORMAP) != 0)
  {
     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 != 0)
  {
     /* 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) == 0)
        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) == 0)
     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 != 0)
  {
     png_uint_16 le = 0x0001;

     if ((*(png_const_bytep) & le) != 0)
        png_set_swap(png_ptr);
  }

#   ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED
     if ((format & PNG_FORMAT_FLAG_BGR) != 0)
     {
        if (colormap == 0 && (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) != 0)
     {
        if (colormap == 0 && (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 != 0 && 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 != 0)
        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.
      */
#   ifdef PNG_WRITE_CUSTOMIZE_COMPRESSION_SUPPORTED
     png_set_compression_level(png_ptr, 3);
#   endif
  }

  /* 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 != 0 && (alpha != 0 || display->convert_to_8bit != 0))
  {
     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 != 0)
        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 == 0)
        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;

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

  png_write_end(png_ptr, info_ptr);
  return 1;
}


static void (PNGCBAPI
image_memory_write)(png_structp png_ptr, png_bytep/*const*/ data, size_t size)
{
  png_image_write_control *display = png_voidcast(png_image_write_control*,
      png_ptr->io_ptr/*backdoor: png_get_io_ptr(png_ptr)*/);
  png_alloc_size_t ob = display->output_bytes;

  /* Check for overflow; this should never happen: */
  if (size <= ((png_alloc_size_t)-1) - ob)
  {
     /* I don't think libpng ever does this, but just in case: */
     if (size > 0)
     {
        if (display->memory_bytes >= ob+size) /* writing */
           memcpy(display->memory+ob, data, size);

        /* Always update the size: */
        display->output_bytes = ob+size;
     }
  }

  else
     png_error(png_ptr, "png_image_write_to_memory: PNG too big");
}

static void (PNGCBAPI
image_memory_flush)(png_structp png_ptr)
{
  PNG_UNUSED(png_ptr)
}

static int
png_image_write_memory(png_voidp argument)
{
  png_image_write_control *display = png_voidcast(png_image_write_control*,
      argument);

  /* The rest of the memory-specific init and write_main in an error protected
   * environment.  This case needs to use callbacks for the write operations
   * since libpng has no built in support for writing to memory.
   */
  png_set_write_fn(display->image->opaque->png_ptr, display/*io_ptr*/,
      image_memory_write, image_memory_flush);

  return png_image_write_main(display);
}

int PNGAPI
png_image_write_to_memory(png_imagep image, void *memory,
   png_alloc_size_t * PNG_RESTRICT memory_bytes, int convert_to_8bit,
   const void *buffer, png_int_32 row_stride, const void *colormap)
{
  /* Write the image to the given buffer, or count the bytes if it is NULL */
  if (image != NULL && image->version == PNG_IMAGE_VERSION)
  {
     if (memory_bytes != NULL && buffer != NULL)
     {
        /* This is to give the caller an easier error detection in the NULL
         * case and guard against uninitialized variable problems:
         */
        if (memory == NULL)
           *memory_bytes = 0;

        if (png_image_write_init(image) != 0)
        {
           png_image_write_control display;
           int result;

           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;
           display.memory = png_voidcast(png_bytep, memory);
           display.memory_bytes = *memory_bytes;
           display.output_bytes = 0;

           result = png_safe_execute(image, png_image_write_memory, &display);
           png_image_free(image);

           /* write_memory returns true even if we ran out of buffer. */
           if (result)
           {
              /* On out-of-buffer this function returns '0' but still updates
               * memory_bytes:
               */
              if (memory != NULL && display.output_bytes > *memory_bytes)
                 result = 0;

              *memory_bytes = display.output_bytes;
           }

           return result;
        }

        else
           return 0;
     }

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

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

  else
     return 0;
}

#ifdef PNG_SIMPLIFIED_WRITE_STDIO_SUPPORTED
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 object. */
  if (image != NULL && image->version == PNG_IMAGE_VERSION)
  {
     if (file != NULL && buffer != NULL)
     {
        if (png_image_write_init(image) != 0)
        {
           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 && buffer != 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) != 0)
           {
              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 /* SIMPLIFIED_WRITE_STDIO */
#endif /* SIMPLIFIED_WRITE */

#ifdef PNG_WRITE_APNG_SUPPORTED
void PNGAPI
png_write_frame_head(png_structp png_ptr, png_infop info_ptr,
   png_bytepp row_pointers, png_uint_32 width, png_uint_32 height,
   png_uint_32 x_offset, png_uint_32 y_offset,
   png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,
   png_byte blend_op)
{
   png_debug(1, "in png_write_frame_head");

   /* there is a chance this has been set after png_write_info was called,
   * so it would be set but not written. is there a way to be sure? */
   if ((info_ptr->valid & PNG_INFO_acTL) == 0)
       png_error(png_ptr, "png_write_frame_head(): acTL not set");

   png_write_reset(png_ptr);

   png_write_reinit(png_ptr, info_ptr, width, height);

   if ((png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN) == 0 ||
       png_ptr->num_frames_written != 0)
       png_write_fcTL(png_ptr, width, height, x_offset, y_offset,
                      delay_num, delay_den, dispose_op, blend_op);

   PNG_UNUSED(row_pointers)
}

void PNGAPI
png_write_frame_tail(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_write_frame_tail");

   png_ptr->num_frames_written++;

   PNG_UNUSED(info_ptr)
}
#endif /* WRITE_APNG */
#endif /* WRITE */