code:
/* pngpread.c - read a png file in push mode
 *
 * Last changed in libpng 1.4.3 [June 26, 2010]
 * Copyright (c) 1998-2010 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
 */

#define PNG_NO_PEDANTIC_WARNINGS
#include "png.h"
#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
#include "pngpriv.h"

/* Push model modes */
#define PNG_READ_SIG_MODE   0
#define PNG_READ_CHUNK_MODE 1
#define PNG_READ_IDAT_MODE  2
#define PNG_SKIP_MODE       3
#define PNG_READ_tEXt_MODE  4
#define PNG_READ_zTXt_MODE  5
#define PNG_READ_DONE_MODE  6
#define PNG_READ_iTXt_MODE  7
#define PNG_ERROR_MODE      8

void PNGAPI
png_process_data(png_structp png_ptr, png_infop info_ptr,
   png_bytep buffer, png_size_t buffer_size)
{
   if (png_ptr == NULL || info_ptr == NULL)
      return;

   png_push_restore_buffer(png_ptr, buffer, buffer_size);

   while (png_ptr->buffer_size)
   {
      png_process_some_data(png_ptr, info_ptr);
   }
}

/* What we do with the incoming data depends on what we were previously
 * doing before we ran out of data...
 */
void /* PRIVATE */
png_process_some_data(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr == NULL)
      return;

   switch (png_ptr->process_mode)
   {
      case PNG_READ_SIG_MODE:
      {
         png_push_read_sig(png_ptr, info_ptr);
         break;
      }

      case PNG_READ_CHUNK_MODE:
      {
         png_push_read_chunk(png_ptr, info_ptr);
         break;
      }

      case PNG_READ_IDAT_MODE:
      {
         png_push_read_IDAT(png_ptr);
         break;
      }

#ifdef PNG_READ_tEXt_SUPPORTED
      case PNG_READ_tEXt_MODE:
      {
         png_push_read_tEXt(png_ptr, info_ptr);
         break;
      }

#endif
#ifdef PNG_READ_zTXt_SUPPORTED
      case PNG_READ_zTXt_MODE:
      {
         png_push_read_zTXt(png_ptr, info_ptr);
         break;
      }

#endif
#ifdef PNG_READ_iTXt_SUPPORTED
      case PNG_READ_iTXt_MODE:
      {
         png_push_read_iTXt(png_ptr, info_ptr);
         break;
      }

#endif
      case PNG_SKIP_MODE:
      {
         png_push_crc_finish(png_ptr);
         break;
      }

      default:
      {
         png_ptr->buffer_size = 0;
         break;
      }
   }
}

/* Read any remaining signature bytes from the stream and compare them with
 * the correct PNG signature.  It is possible that this routine is called
 * with bytes already read from the signature, either because they have been
 * checked by the calling application, or because of multiple calls to this
 * routine.
 */
void /* PRIVATE */
png_push_read_sig(png_structp png_ptr, png_infop info_ptr)
{
   png_size_t num_checked = png_ptr->sig_bytes,
             num_to_check = 8 - num_checked;

   if (png_ptr->buffer_size < num_to_check)
   {
      num_to_check = png_ptr->buffer_size;
   }

   png_push_fill_buffer(png_ptr, &(info_ptr->signature[num_checked]),
      num_to_check);
   png_ptr->sig_bytes = (png_byte)(png_ptr->sig_bytes + num_to_check);

   if (png_sig_cmp(info_ptr->signature, num_checked, num_to_check))
   {
      if (num_checked < 4 &&
          png_sig_cmp(info_ptr->signature, num_checked, num_to_check - 4))
         png_error(png_ptr, "Not a PNG file");
      else
         png_error(png_ptr, "PNG file corrupted by ASCII conversion");
   }
   else
   {
      if (png_ptr->sig_bytes >= 8)
      {
         png_ptr->process_mode = PNG_READ_CHUNK_MODE;
      }
   }
}

void /* PRIVATE */
png_push_read_chunk(png_structp png_ptr, png_infop info_ptr)
{
      PNG_IHDR;
      PNG_IDAT;
      PNG_IEND;
      PNG_PLTE;
#ifdef PNG_READ_bKGD_SUPPORTED
      PNG_bKGD;
#endif
#ifdef PNG_READ_cHRM_SUPPORTED
      PNG_cHRM;
#endif
#ifdef PNG_READ_gAMA_SUPPORTED
      PNG_gAMA;
#endif
#ifdef PNG_READ_hIST_SUPPORTED
      PNG_hIST;
#endif
#ifdef PNG_READ_iCCP_SUPPORTED
      PNG_iCCP;
#endif
#ifdef PNG_READ_iTXt_SUPPORTED
      PNG_iTXt;
#endif
#ifdef PNG_READ_oFFs_SUPPORTED
      PNG_oFFs;
#endif
#ifdef PNG_READ_pCAL_SUPPORTED
      PNG_pCAL;
#endif
#ifdef PNG_READ_pHYs_SUPPORTED
      PNG_pHYs;
#endif
#ifdef PNG_READ_sBIT_SUPPORTED
      PNG_sBIT;
#endif
#ifdef PNG_READ_sCAL_SUPPORTED
      PNG_sCAL;
#endif
#ifdef PNG_READ_sRGB_SUPPORTED
      PNG_sRGB;
#endif
#ifdef PNG_READ_sPLT_SUPPORTED
      PNG_sPLT;
#endif
#ifdef PNG_READ_tEXt_SUPPORTED
      PNG_tEXt;
#endif
#ifdef PNG_READ_tIME_SUPPORTED
      PNG_tIME;
#endif
#ifdef PNG_READ_tRNS_SUPPORTED
      PNG_tRNS;
#endif
#ifdef PNG_READ_zTXt_SUPPORTED
      PNG_zTXt;
#endif

   /* First we make sure we have enough data for the 4 byte chunk name
    * and the 4 byte chunk length before proceeding with decoding the
    * chunk data.  To fully decode each of these chunks, we also make
    * sure we have enough data in the buffer for the 4 byte CRC at the
    * end of every chunk (except IDAT, which is handled separately).
    */
   if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
   {
      png_byte chunk_length[4];

      if (png_ptr->buffer_size < 8)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_fill_buffer(png_ptr, chunk_length, 4);
      png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
      png_reset_crc(png_ptr);
      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
      png_check_chunk_name(png_ptr, png_ptr->chunk_name);
      png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;
   }

   if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
     if (png_ptr->mode & PNG_AFTER_IDAT)
        png_ptr->mode |= PNG_HAVE_CHUNK_AFTER_IDAT;

   if (!png_memcmp(png_ptr->chunk_name, png_IHDR, 4))
   {
      if (png_ptr->push_length != 13)
         png_error(png_ptr, "Invalid IHDR length");

      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_IHDR(png_ptr, info_ptr, png_ptr->push_length);
   }

   else if (!png_memcmp(png_ptr->chunk_name, png_IEND, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_IEND(png_ptr, info_ptr, png_ptr->push_length);

      png_ptr->process_mode = PNG_READ_DONE_MODE;
      png_push_have_end(png_ptr, info_ptr);
   }

#ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
   else if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
         png_ptr->mode |= PNG_HAVE_IDAT;

      png_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);

      if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
         png_ptr->mode |= PNG_HAVE_PLTE;

      else if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
      {
         if (!(png_ptr->mode & PNG_HAVE_IHDR))
            png_error(png_ptr, "Missing IHDR before IDAT");

         else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
                  !(png_ptr->mode & PNG_HAVE_PLTE))
            png_error(png_ptr, "Missing PLTE before IDAT");
      }
   }

#endif
   else if (!png_memcmp(png_ptr->chunk_name, png_PLTE, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }
      png_handle_PLTE(png_ptr, info_ptr, png_ptr->push_length);
   }

   else if (!png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
   {
      /* If we reach an IDAT chunk, this means we have read all of the
       * header chunks, and we can start reading the image (or if this
       * is called after the image has been read - we have an error).
       */

      if (!(png_ptr->mode & PNG_HAVE_IHDR))
         png_error(png_ptr, "Missing IHDR before IDAT");

      else if (png_ptr->color_type == PNG_COLOR_TYPE_PALETTE &&
          !(png_ptr->mode & PNG_HAVE_PLTE))
         png_error(png_ptr, "Missing PLTE before IDAT");

      if (png_ptr->mode & PNG_HAVE_IDAT)
      {
         if (!(png_ptr->mode & PNG_HAVE_CHUNK_AFTER_IDAT))
            if (png_ptr->push_length == 0)
               return;

         if (png_ptr->mode & PNG_AFTER_IDAT)
            png_benign_error(png_ptr, "Too many IDATs found");
      }

      png_ptr->idat_size = png_ptr->push_length;
      png_ptr->mode |= PNG_HAVE_IDAT;
      png_ptr->process_mode = PNG_READ_IDAT_MODE;
      png_push_have_info(png_ptr, info_ptr);
      png_ptr->zstream.avail_out =
          (uInt) PNG_ROWBYTES(png_ptr->pixel_depth,
          png_ptr->iwidth) + 1;
      png_ptr->zstream.next_out = png_ptr->row_buf;
      return;
   }

#ifdef PNG_READ_gAMA_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_gAMA, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_gAMA(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_sBIT_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_sBIT, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_sBIT(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_cHRM_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_cHRM, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_cHRM(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_sRGB_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_sRGB, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_sRGB(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_iCCP_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_iCCP, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_iCCP(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_sPLT_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_sPLT, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_sPLT(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_tRNS_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_tRNS, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_tRNS(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_bKGD_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_bKGD, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_bKGD(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_hIST_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_hIST, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_hIST(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_pHYs_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_pHYs, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_pHYs(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_oFFs_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_oFFs, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_oFFs(png_ptr, info_ptr, png_ptr->push_length);
   }
#endif

#ifdef PNG_READ_pCAL_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_pCAL, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_pCAL(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_sCAL_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_sCAL, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_sCAL(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_tIME_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_tIME, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_handle_tIME(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_tEXt_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_tEXt, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_zTXt_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_zTXt, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
#ifdef PNG_READ_iTXt_SUPPORTED
   else if (!png_memcmp(png_ptr->chunk_name, png_iTXt, 4))
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);
   }

#endif
   else
   {
      if (png_ptr->push_length + 4 > png_ptr->buffer_size)
      {
         png_push_save_buffer(png_ptr);
         return;
      }
      png_push_handle_unknown(png_ptr, info_ptr, png_ptr->push_length);
   }

   png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
}

void /* PRIVATE */
png_push_crc_skip(png_structp png_ptr, png_uint_32 skip)
{
   png_ptr->process_mode = PNG_SKIP_MODE;
   png_ptr->skip_length = skip;
}

void /* PRIVATE */
png_push_crc_finish(png_structp png_ptr)
{
   if (png_ptr->skip_length && png_ptr->save_buffer_size)
   {
      png_size_t save_size;

      if (png_ptr->skip_length < (png_uint_32)png_ptr->save_buffer_size)
         save_size = (png_size_t)png_ptr->skip_length;
      else
         save_size = png_ptr->save_buffer_size;

      png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);

      png_ptr->skip_length -= save_size;
      png_ptr->buffer_size -= save_size;
      png_ptr->save_buffer_size -= save_size;
      png_ptr->save_buffer_ptr += save_size;
   }
   if (png_ptr->skip_length && png_ptr->current_buffer_size)
   {
      png_size_t save_size;

      if (png_ptr->skip_length < (png_uint_32)png_ptr->current_buffer_size)
         save_size = (png_size_t)png_ptr->skip_length;
      else
         save_size = png_ptr->current_buffer_size;

      png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);

      png_ptr->skip_length -= save_size;
      png_ptr->buffer_size -= save_size;
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
   if (!png_ptr->skip_length)
   {
      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_crc_finish(png_ptr, 0);
      png_ptr->process_mode = PNG_READ_CHUNK_MODE;
   }
}

void PNGAPI
png_push_fill_buffer(png_structp png_ptr, png_bytep buffer, png_size_t length)
{
   png_bytep ptr;

   if (png_ptr == NULL)
      return;

   ptr = buffer;
   if (png_ptr->save_buffer_size)
   {
      png_size_t save_size;

      if (length < png_ptr->save_buffer_size)
         save_size = length;
      else
         save_size = png_ptr->save_buffer_size;

      png_memcpy(ptr, png_ptr->save_buffer_ptr, save_size);
      length -= save_size;
      ptr += save_size;
      png_ptr->buffer_size -= save_size;
      png_ptr->save_buffer_size -= save_size;
      png_ptr->save_buffer_ptr += save_size;
   }
   if (length && png_ptr->current_buffer_size)
   {
      png_size_t save_size;

      if (length < png_ptr->current_buffer_size)
         save_size = length;

      else
         save_size = png_ptr->current_buffer_size;

      png_memcpy(ptr, png_ptr->current_buffer_ptr, save_size);
      png_ptr->buffer_size -= save_size;
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
}

void /* PRIVATE */
png_push_save_buffer(png_structp png_ptr)
{
   if (png_ptr->save_buffer_size)
   {
      if (png_ptr->save_buffer_ptr != png_ptr->save_buffer)
      {
         png_size_t i, istop;
         png_bytep sp;
         png_bytep dp;

         istop = png_ptr->save_buffer_size;
         for (i = 0, sp = png_ptr->save_buffer_ptr, dp = png_ptr->save_buffer;
            i < istop; i++, sp++, dp++)
         {
            *dp = *sp;
         }
      }
   }
   if (png_ptr->save_buffer_size + png_ptr->current_buffer_size >
      png_ptr->save_buffer_max)
   {
      png_size_t new_max;
      png_bytep old_buffer;

      if (png_ptr->save_buffer_size > PNG_SIZE_MAX -
         (png_ptr->current_buffer_size + 256))
      {
        png_error(png_ptr, "Potential overflow of save_buffer");
      }

      new_max = png_ptr->save_buffer_size + png_ptr->current_buffer_size + 256;
      old_buffer = png_ptr->save_buffer;
      png_ptr->save_buffer = (png_bytep)png_malloc_warn(png_ptr,
         (png_size_t)new_max);
      if (png_ptr->save_buffer == NULL)
      {
        png_free(png_ptr, old_buffer);
        png_error(png_ptr, "Insufficient memory for save_buffer");
      }
      png_memcpy(png_ptr->save_buffer, old_buffer, png_ptr->save_buffer_size);
      png_free(png_ptr, old_buffer);
      png_ptr->save_buffer_max = new_max;
   }
   if (png_ptr->current_buffer_size)
   {
      png_memcpy(png_ptr->save_buffer + png_ptr->save_buffer_size,
         png_ptr->current_buffer_ptr, png_ptr->current_buffer_size);
      png_ptr->save_buffer_size += png_ptr->current_buffer_size;
      png_ptr->current_buffer_size = 0;
   }
   png_ptr->save_buffer_ptr = png_ptr->save_buffer;
   png_ptr->buffer_size = 0;
}

void /* PRIVATE */
png_push_restore_buffer(png_structp png_ptr, png_bytep buffer,
   png_size_t buffer_length)
{
   png_ptr->current_buffer = buffer;
   png_ptr->current_buffer_size = buffer_length;
   png_ptr->buffer_size = buffer_length + png_ptr->save_buffer_size;
   png_ptr->current_buffer_ptr = png_ptr->current_buffer;
}

void /* PRIVATE */
png_push_read_IDAT(png_structp png_ptr)
{
   PNG_IDAT;
   if (!(png_ptr->mode & PNG_HAVE_CHUNK_HEADER))
   {
      png_byte chunk_length[4];

      if (png_ptr->buffer_size < 8)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_fill_buffer(png_ptr, chunk_length, 4);
      png_ptr->push_length = png_get_uint_31(png_ptr, chunk_length);
      png_reset_crc(png_ptr);
      png_crc_read(png_ptr, png_ptr->chunk_name, 4);
      png_ptr->mode |= PNG_HAVE_CHUNK_HEADER;

      if (png_memcmp(png_ptr->chunk_name, png_IDAT, 4))
      {
         png_ptr->process_mode = PNG_READ_CHUNK_MODE;
         if (!(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
            png_error(png_ptr, "Not enough compressed data");
         return;
      }

      png_ptr->idat_size = png_ptr->push_length;
   }
   if (png_ptr->idat_size && png_ptr->save_buffer_size)
   {
      png_size_t save_size;

      if (png_ptr->idat_size < (png_uint_32)png_ptr->save_buffer_size)
      {
         save_size = (png_size_t)png_ptr->idat_size;

         /* Check for overflow */
         if ((png_uint_32)save_size != png_ptr->idat_size)
            png_error(png_ptr, "save_size overflowed in pngpread");
      }
      else
         save_size = png_ptr->save_buffer_size;

      png_calculate_crc(png_ptr, png_ptr->save_buffer_ptr, save_size);

      png_process_IDAT_data(png_ptr, png_ptr->save_buffer_ptr, save_size);

      png_ptr->idat_size -= save_size;
      png_ptr->buffer_size -= save_size;
      png_ptr->save_buffer_size -= save_size;
      png_ptr->save_buffer_ptr += save_size;
   }
   if (png_ptr->idat_size && png_ptr->current_buffer_size)
   {
      png_size_t save_size;

      if (png_ptr->idat_size < (png_uint_32)png_ptr->current_buffer_size)
      {
         save_size = (png_size_t)png_ptr->idat_size;

         /* Check for overflow */
         if ((png_uint_32)save_size != png_ptr->idat_size)
            png_error(png_ptr, "save_size overflowed in pngpread");
      }
      else
         save_size = png_ptr->current_buffer_size;

      png_calculate_crc(png_ptr, png_ptr->current_buffer_ptr, save_size);

      png_process_IDAT_data(png_ptr, png_ptr->current_buffer_ptr, save_size);

      png_ptr->idat_size -= save_size;
      png_ptr->buffer_size -= save_size;
      png_ptr->current_buffer_size -= save_size;
      png_ptr->current_buffer_ptr += save_size;
   }
   if (!png_ptr->idat_size)
   {
      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_crc_finish(png_ptr, 0);
      png_ptr->mode &= ~PNG_HAVE_CHUNK_HEADER;
      png_ptr->mode |= PNG_AFTER_IDAT;
   }
}

void /* PRIVATE */
png_process_IDAT_data(png_structp png_ptr, png_bytep buffer,
   png_size_t buffer_length)
{
   /* The caller checks for a non-zero buffer length. */
   if (!(buffer_length > 0) || buffer == NULL)
      png_error(png_ptr, "No IDAT data (internal error)");

   /* This routine must process all the data it has been given
    * before returning, calling the row callback as required to
    * handle the uncompressed results.
    */
   png_ptr->zstream.next_in = buffer;
   png_ptr->zstream.avail_in = (uInt)buffer_length;

   /* Keep going until the decompressed data is all processed
    * or the stream marked as finished.
    */
   while (png_ptr->zstream.avail_in > 0 &&
      !(png_ptr->flags & PNG_FLAG_ZLIB_FINISHED))
   {
      int ret;

      /* We have data for zlib, but we must check that zlib
       * has somewhere to put the results.  It doesn't matter
       * if we don't expect any results -- it may be the input
       * data is just the LZ end code.
       */
      if (!(png_ptr->zstream.avail_out > 0))
      {
         png_ptr->zstream.avail_out =
             (uInt) PNG_ROWBYTES(png_ptr->pixel_depth,
             png_ptr->iwidth) + 1;
         png_ptr->zstream.next_out = png_ptr->row_buf;
      }

      /* Using Z_SYNC_FLUSH here means that an unterminated
       * LZ stream can still be handled (a stream with a missing
       * end code), otherwise (Z_NO_FLUSH) a future zlib
       * implementation might defer output and, therefore,
       * change the current behavior.  (See comments in inflate.c
       * for why this doesn't happen at present with zlib 1.2.5.)
       */
      ret = inflate(&png_ptr->zstream, Z_SYNC_FLUSH);

      /* Check for any failure before proceeding. */
      if (ret != Z_OK && ret != Z_STREAM_END)
      {
         /* Terminate the decompression. */
         png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;

         /* This may be a truncated stream (missing or
          * damaged end code).  Treat that as a warning.
          */
         if (png_ptr->row_number >= png_ptr->num_rows ||
             png_ptr->pass > 6)
            png_warning(png_ptr, "Truncated compressed data in IDAT");
         else
            png_error(png_ptr, "Decompression error in IDAT");

         /* Skip the check on unprocessed input */
         return;
      }

      /* Did inflate output any data? */
      if (png_ptr->zstream.next_out != png_ptr->row_buf)
      {
         /* Is this unexpected data after the last row?
          * If it is, artificially terminate the LZ output
          * here.
          */
         if (png_ptr->row_number >= png_ptr->num_rows ||
             png_ptr->pass > 6)
         {
            /* Extra data. */
            png_warning(png_ptr, "Extra compressed data in IDAT");
            png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
            /* Do no more processing; skip the unprocessed
             * input check below.
             */
            return;
         }

         /* Do we have a complete row? */
         if (png_ptr->zstream.avail_out == 0)
            png_push_process_row(png_ptr);
      }

      /* And check for the end of the stream. */
      if (ret == Z_STREAM_END)
         png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
   }

   /* All the data should have been processed, if anything
    * is left at this point we have bytes of IDAT data
    * after the zlib end code.
    */
   if (png_ptr->zstream.avail_in > 0)
      png_warning(png_ptr, "Extra compression data");
}

void /* PRIVATE */
png_push_process_row(png_structp png_ptr)
{
   png_ptr->row_info.color_type = png_ptr->color_type;
   png_ptr->row_info.width = png_ptr->iwidth;
   png_ptr->row_info.channels = png_ptr->channels;
   png_ptr->row_info.bit_depth = png_ptr->bit_depth;
   png_ptr->row_info.pixel_depth = png_ptr->pixel_depth;

   png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
       png_ptr->row_info.width);

   png_read_filter_row(png_ptr, &(png_ptr->row_info),
       png_ptr->row_buf + 1, png_ptr->prev_row + 1,
       (int)(png_ptr->row_buf[0]));

   png_memcpy(png_ptr->prev_row, png_ptr->row_buf, png_ptr->rowbytes + 1);

   if (png_ptr->transformations || (png_ptr->flags&PNG_FLAG_STRIP_ALPHA))
      png_do_read_transformations(png_ptr);

#ifdef PNG_READ_INTERLACING_SUPPORTED
   /* Blow up interlaced rows to full size */
   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
   {
      if (png_ptr->pass < 6)
/*       old interface (pre-1.0.9):
         png_do_read_interlace(&(png_ptr->row_info),
             png_ptr->row_buf + 1, png_ptr->pass, png_ptr->transformations);
 */
         png_do_read_interlace(png_ptr);

    switch (png_ptr->pass)
    {
         case 0:
         {
            int i;
            for (i = 0; i < 8 && png_ptr->pass == 0; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr); /* Updates png_ptr->pass */
            }

            if (png_ptr->pass == 2) /* Pass 1 might be empty */
            {
               for (i = 0; i < 4 && png_ptr->pass == 2; i++)
               {
                  png_push_have_row(png_ptr, NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }

            if (png_ptr->pass == 4 && png_ptr->height <= 4)
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }

            if (png_ptr->pass == 6 && png_ptr->height <= 4)
            {
                png_push_have_row(png_ptr, NULL);
                png_read_push_finish_row(png_ptr);
            }

            break;
         }

         case 1:
         {
            int i;
            for (i = 0; i < 8 && png_ptr->pass == 1; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }

            if (png_ptr->pass == 2) /* Skip top 4 generated rows */
            {
               for (i = 0; i < 4 && png_ptr->pass == 2; i++)
               {
                  png_push_have_row(png_ptr, NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }

            break;
         }

         case 2:
         {
            int i;

            for (i = 0; i < 4 && png_ptr->pass == 2; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }

            for (i = 0; i < 4 && png_ptr->pass == 2; i++)
            {
               png_push_have_row(png_ptr, NULL);
               png_read_push_finish_row(png_ptr);
            }

            if (png_ptr->pass == 4) /* Pass 3 might be empty */
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }

            break;
         }

         case 3:
         {
            int i;

            for (i = 0; i < 4 && png_ptr->pass == 3; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }

            if (png_ptr->pass == 4) /* Skip top two generated rows */
            {
               for (i = 0; i < 2 && png_ptr->pass == 4; i++)
               {
                  png_push_have_row(png_ptr, NULL);
                  png_read_push_finish_row(png_ptr);
               }
            }

            break;
         }

         case 4:
         {
            int i;

            for (i = 0; i < 2 && png_ptr->pass == 4; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }

            for (i = 0; i < 2 && png_ptr->pass == 4; i++)
            {
               png_push_have_row(png_ptr, NULL);
               png_read_push_finish_row(png_ptr);
            }

            if (png_ptr->pass == 6) /* Pass 5 might be empty */
            {
               png_push_have_row(png_ptr, NULL);
               png_read_push_finish_row(png_ptr);
            }

            break;
         }

         case 5:
         {
            int i;

            for (i = 0; i < 2 && png_ptr->pass == 5; i++)
            {
               png_push_have_row(png_ptr, png_ptr->row_buf + 1);
               png_read_push_finish_row(png_ptr);
            }

            if (png_ptr->pass == 6) /* Skip top generated row */
            {
               png_push_have_row(png_ptr, NULL);
               png_read_push_finish_row(png_ptr);
            }

            break;
         }

         default:
         case 6:
         {
            png_push_have_row(png_ptr, png_ptr->row_buf + 1);
            png_read_push_finish_row(png_ptr);

            if (png_ptr->pass != 6)
               break;

            png_push_have_row(png_ptr, NULL);
            png_read_push_finish_row(png_ptr);
         }
      }
   }
   else
#endif
   {
      png_push_have_row(png_ptr, png_ptr->row_buf + 1);
      png_read_push_finish_row(png_ptr);
   }
}

void /* PRIVATE */
png_read_push_finish_row(png_structp png_ptr)
{
   /* Arrays to facilitate easy interlacing - use pass (0 - 6) as index */

   /* Start of interlace block */
   PNG_CONST int FARDATA png_pass_start[] = {0, 4, 0, 2, 0, 1, 0};

   /* Offset to next interlace block */
   PNG_CONST int FARDATA png_pass_inc[] = {8, 8, 4, 4, 2, 2, 1};

   /* Start of interlace block in the y direction */
   PNG_CONST int FARDATA png_pass_ystart[] = {0, 0, 4, 0, 2, 0, 1};

   /* Offset to next interlace block in the y direction */
   PNG_CONST int FARDATA png_pass_yinc[] = {8, 8, 8, 4, 4, 2, 2};

   /* Height of interlace block.  This is not currently used - if you need
    * it, uncomment it here and in png.h
   PNG_CONST int FARDATA png_pass_height[] = {8, 8, 4, 4, 2, 2, 1};
   */

   png_ptr->row_number++;
   if (png_ptr->row_number < png_ptr->num_rows)
      return;

#ifdef PNG_READ_INTERLACING_SUPPORTED
   if (png_ptr->interlaced)
   {
      png_ptr->row_number = 0;
      png_memset(png_ptr->prev_row, 0,
         png_ptr->rowbytes + 1);
      do
      {
         png_ptr->pass++;
         if ((png_ptr->pass == 1 && png_ptr->width < 5) ||
             (png_ptr->pass == 3 && png_ptr->width < 3) ||
             (png_ptr->pass == 5 && png_ptr->width < 2))
           png_ptr->pass++;

         if (png_ptr->pass > 7)
            png_ptr->pass--;

         if (png_ptr->pass >= 7)
            break;

         png_ptr->iwidth = (png_ptr->width +
            png_pass_inc[png_ptr->pass] - 1 -
            png_pass_start[png_ptr->pass]) /
            png_pass_inc[png_ptr->pass];

         if (png_ptr->transformations & PNG_INTERLACE)
            break;

         png_ptr->num_rows = (png_ptr->height +
            png_pass_yinc[png_ptr->pass] - 1 -
            png_pass_ystart[png_ptr->pass]) /
            png_pass_yinc[png_ptr->pass];

      } while (png_ptr->iwidth == 0 || png_ptr->num_rows == 0);
   }
#endif /* PNG_READ_INTERLACING_SUPPORTED */
}

#ifdef PNG_READ_tEXt_SUPPORTED
void /* PRIVATE */
png_push_handle_tEXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
      {
         png_error(png_ptr, "Out of place tEXt");
         info_ptr = info_ptr; /* To quiet some compiler warnings */
      }

#ifdef PNG_MAX_MALLOC_64K
   png_ptr->skip_length = 0;  /* This may not be necessary */

   if (length > (png_uint_32)65535L) /* Can't hold entire string in memory */
   {
      png_warning(png_ptr, "tEXt chunk too large to fit in memory");
      png_ptr->skip_length = length - (png_uint_32)65535L;
      length = (png_uint_32)65535L;
   }
#endif

   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
      (png_size_t)(length + 1));
   png_ptr->current_text[length] = '\0';
   png_ptr->current_text_ptr = png_ptr->current_text;
   png_ptr->current_text_size = (png_size_t)length;
   png_ptr->current_text_left = (png_size_t)length;
   png_ptr->process_mode = PNG_READ_tEXt_MODE;
}

void /* PRIVATE */
png_push_read_tEXt(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr->buffer_size && png_ptr->current_text_left)
   {
      png_size_t text_size;

      if (png_ptr->buffer_size < png_ptr->current_text_left)
         text_size = png_ptr->buffer_size;

      else
         text_size = png_ptr->current_text_left;

      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
      png_ptr->current_text_left -= text_size;
      png_ptr->current_text_ptr += text_size;
   }
   if (!(png_ptr->current_text_left))
   {
      png_textp text_ptr;
      png_charp text;
      png_charp key;
      int ret;

      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_crc_finish(png_ptr);

#ifdef PNG_MAX_MALLOC_64K
      if (png_ptr->skip_length)
         return;
#endif

      key = png_ptr->current_text;

      for (text = key; *text; text++)
         /* Empty loop */ ;

      if (text < key + png_ptr->current_text_size)
         text++;

      text_ptr = (png_textp)png_malloc(png_ptr,
         png_sizeof(png_text));
      text_ptr->compression = PNG_TEXT_COMPRESSION_NONE;
      text_ptr->key = key;
#ifdef PNG_iTXt_SUPPORTED
      text_ptr->lang = NULL;
      text_ptr->lang_key = NULL;
#endif
      text_ptr->text = text;

      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);

      png_free(png_ptr, key);
      png_free(png_ptr, text_ptr);
      png_ptr->current_text = NULL;

      if (ret)
        png_warning(png_ptr, "Insufficient memory to store text chunk");
   }
}
#endif

#ifdef PNG_READ_zTXt_SUPPORTED
void /* PRIVATE */
png_push_handle_zTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
      {
         png_error(png_ptr, "Out of place zTXt");
         info_ptr = info_ptr; /* To quiet some compiler warnings */
      }

#ifdef PNG_MAX_MALLOC_64K
   /* We can't handle zTXt chunks > 64K, since we don't have enough space
    * to be able to store the uncompressed data.  Actually, the threshold
    * is probably around 32K, but it isn't as definite as 64K is.
    */
   if (length > (png_uint_32)65535L)
   {
      png_warning(png_ptr, "zTXt chunk too large to fit in memory");
      png_push_crc_skip(png_ptr, length);
      return;
   }
#endif

   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
      (png_size_t)(length + 1));
   png_ptr->current_text[length] = '\0';
   png_ptr->current_text_ptr = png_ptr->current_text;
   png_ptr->current_text_size = (png_size_t)length;
   png_ptr->current_text_left = (png_size_t)length;
   png_ptr->process_mode = PNG_READ_zTXt_MODE;
}

void /* PRIVATE */
png_push_read_zTXt(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr->buffer_size && png_ptr->current_text_left)
   {
      png_size_t text_size;

      if (png_ptr->buffer_size < (png_uint_32)png_ptr->current_text_left)
         text_size = png_ptr->buffer_size;

      else
         text_size = png_ptr->current_text_left;

      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
      png_ptr->current_text_left -= text_size;
      png_ptr->current_text_ptr += text_size;
   }
   if (!(png_ptr->current_text_left))
   {
      png_textp text_ptr;
      png_charp text;
      png_charp key;
      int ret;
      png_size_t text_size, key_size;

      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_crc_finish(png_ptr);

      key = png_ptr->current_text;

      for (text = key; *text; text++)
         /* Empty loop */ ;

      /* zTXt can't have zero text */
      if (text >= key + png_ptr->current_text_size)
      {
         png_ptr->current_text = NULL;
         png_free(png_ptr, key);
         return;
      }

      text++;

      if (*text != PNG_TEXT_COMPRESSION_zTXt) /* Check compression byte */
      {
         png_ptr->current_text = NULL;
         png_free(png_ptr, key);
         return;
      }

      text++;

      png_ptr->zstream.next_in = (png_bytep )text;
      png_ptr->zstream.avail_in = (uInt)(png_ptr->current_text_size -
         (text - key));
      png_ptr->zstream.next_out = png_ptr->zbuf;
      png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;

      key_size = text - key;
      text_size = 0;
      text = NULL;
      ret = Z_STREAM_END;

      while (png_ptr->zstream.avail_in)
      {
         ret = inflate(&png_ptr->zstream, Z_PARTIAL_FLUSH);
         if (ret != Z_OK && ret != Z_STREAM_END)
         {
            inflateReset(&png_ptr->zstream);
            png_ptr->zstream.avail_in = 0;
            png_ptr->current_text = NULL;
            png_free(png_ptr, key);
            png_free(png_ptr, text);
            return;
         }
         if (!(png_ptr->zstream.avail_out) || ret == Z_STREAM_END)
         {
            if (text == NULL)
            {
               text = (png_charp)png_malloc(png_ptr,
                     (png_ptr->zbuf_size
                     - png_ptr->zstream.avail_out + key_size + 1));

               png_memcpy(text + key_size, png_ptr->zbuf,
                  png_ptr->zbuf_size - png_ptr->zstream.avail_out);

               png_memcpy(text, key, key_size);

               text_size = key_size + png_ptr->zbuf_size -
                  png_ptr->zstream.avail_out;

               *(text + text_size) = '\0';
            }
            else
            {
               png_charp tmp;

               tmp = text;
               text = (png_charp)png_malloc(png_ptr, text_size +
                  (png_ptr->zbuf_size
                  - png_ptr->zstream.avail_out + 1));

               png_memcpy(text, tmp, text_size);
               png_free(png_ptr, tmp);

               png_memcpy(text + text_size, png_ptr->zbuf,
                  png_ptr->zbuf_size - png_ptr->zstream.avail_out);

               text_size += png_ptr->zbuf_size - png_ptr->zstream.avail_out;
               *(text + text_size) = '\0';
            }
            if (ret != Z_STREAM_END)
            {
               png_ptr->zstream.next_out = png_ptr->zbuf;
               png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;
            }
         }
         else
         {
            break;
         }

         if (ret == Z_STREAM_END)
            break;
      }

      inflateReset(&png_ptr->zstream);
      png_ptr->zstream.avail_in = 0;

      if (ret != Z_STREAM_END)
      {
         png_ptr->current_text = NULL;
         png_free(png_ptr, key);
         png_free(png_ptr, text);
         return;
      }

      png_ptr->current_text = NULL;
      png_free(png_ptr, key);
      key = text;
      text += key_size;

      text_ptr = (png_textp)png_malloc(png_ptr,
          png_sizeof(png_text));
      text_ptr->compression = PNG_TEXT_COMPRESSION_zTXt;
      text_ptr->key = key;
#ifdef PNG_iTXt_SUPPORTED
      text_ptr->lang = NULL;
      text_ptr->lang_key = NULL;
#endif
      text_ptr->text = text;

      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);

      png_free(png_ptr, key);
      png_free(png_ptr, text_ptr);

      if (ret)
        png_warning(png_ptr, "Insufficient memory to store text chunk");
   }
}
#endif

#ifdef PNG_READ_iTXt_SUPPORTED
void /* PRIVATE */
png_push_handle_iTXt(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   if (!(png_ptr->mode & PNG_HAVE_IHDR) || (png_ptr->mode & PNG_HAVE_IEND))
      {
         png_error(png_ptr, "Out of place iTXt");
         info_ptr = info_ptr; /* To quiet some compiler warnings */
      }

#ifdef PNG_MAX_MALLOC_64K
   png_ptr->skip_length = 0;  /* This may not be necessary */

   if (length > (png_uint_32)65535L) /* Can't hold entire string in memory */
   {
      png_warning(png_ptr, "iTXt chunk too large to fit in memory");
      png_ptr->skip_length = length - (png_uint_32)65535L;
      length = (png_uint_32)65535L;
   }
#endif

   png_ptr->current_text = (png_charp)png_malloc(png_ptr,
      (png_size_t)(length + 1));
   png_ptr->current_text[length] = '\0';
   png_ptr->current_text_ptr = png_ptr->current_text;
   png_ptr->current_text_size = (png_size_t)length;
   png_ptr->current_text_left = (png_size_t)length;
   png_ptr->process_mode = PNG_READ_iTXt_MODE;
}

void /* PRIVATE */
png_push_read_iTXt(png_structp png_ptr, png_infop info_ptr)
{

   if (png_ptr->buffer_size && png_ptr->current_text_left)
   {
      png_size_t text_size;

      if (png_ptr->buffer_size < png_ptr->current_text_left)
         text_size = png_ptr->buffer_size;

      else
         text_size = png_ptr->current_text_left;

      png_crc_read(png_ptr, (png_bytep)png_ptr->current_text_ptr, text_size);
      png_ptr->current_text_left -= text_size;
      png_ptr->current_text_ptr += text_size;
   }
   if (!(png_ptr->current_text_left))
   {
      png_textp text_ptr;
      png_charp key;
      int comp_flag;
      png_charp lang;
      png_charp lang_key;
      png_charp text;
      int ret;

      if (png_ptr->buffer_size < 4)
      {
         png_push_save_buffer(png_ptr);
         return;
      }

      png_push_crc_finish(png_ptr);

#ifdef PNG_MAX_MALLOC_64K
      if (png_ptr->skip_length)
         return;
#endif

      key = png_ptr->current_text;

      for (lang = key; *lang; lang++)
         /* Empty loop */ ;

      if (lang < key + png_ptr->current_text_size - 3)
         lang++;

      comp_flag = *lang++;
      lang++;     /* Skip comp_type, always zero */

      for (lang_key = lang; *lang_key; lang_key++)
         /* Empty loop */ ;

      lang_key++;        /* Skip NUL separator */

      text=lang_key;

      if (lang_key < key + png_ptr->current_text_size - 1)
      {
        for (; *text; text++)
           /* Empty loop */ ;
      }

      if (text < key + png_ptr->current_text_size)
         text++;

      text_ptr = (png_textp)png_malloc(png_ptr,
         png_sizeof(png_text));

      text_ptr->compression = comp_flag + 2;
      text_ptr->key = key;
      text_ptr->lang = lang;
      text_ptr->lang_key = lang_key;
      text_ptr->text = text;
      text_ptr->text_length = 0;
      text_ptr->itxt_length = png_strlen(text);

      ret = png_set_text_2(png_ptr, info_ptr, text_ptr, 1);

      png_ptr->current_text = NULL;

      png_free(png_ptr, text_ptr);
      if (ret)
         png_warning(png_ptr, "Insufficient memory to store iTXt chunk");
   }
}
#endif

/* This function is called when we haven't found a handler for this
 * chunk.  If there isn't a problem with the chunk itself (ie a bad chunk
 * name or a critical chunk), the chunk is (currently) silently ignored.
 */
void /* PRIVATE */
png_push_handle_unknown(png_structp png_ptr, png_infop info_ptr, png_uint_32
   length)
{
   png_uint_32 skip = 0;

   if (!(png_ptr->chunk_name[0] & 0x20))
   {
#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
      if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
         PNG_HANDLE_CHUNK_ALWAYS
#ifdef PNG_READ_USER_CHUNKS_SUPPORTED
         && png_ptr->read_user_chunk_fn == NULL
#endif
         )
#endif
         png_chunk_error(png_ptr, "unknown critical chunk");

      info_ptr = info_ptr; /* To quiet some compiler warnings */
   }

#ifdef PNG_READ_UNKNOWN_CHUNKS_SUPPORTED
   if (png_ptr->flags & PNG_FLAG_KEEP_UNKNOWN_CHUNKS)
   {
#ifdef PNG_MAX_MALLOC_64K
      if (length > (png_uint_32)65535L)
      {
          png_warning(png_ptr, "unknown chunk too large to fit in memory");
          skip = length - (png_uint_32)65535L;
          length = (png_uint_32)65535L;
      }
#endif
      png_memcpy((png_charp)png_ptr->unknown_chunk.name,
                 (png_charp)png_ptr->chunk_name,
                 png_sizeof(png_ptr->unknown_chunk.name));
      png_ptr->unknown_chunk.name[png_sizeof(png_ptr->unknown_chunk.name) - 1]
        = '\0';

      png_ptr->unknown_chunk.size = (png_size_t)length;

      if (length == 0)
         png_ptr->unknown_chunk.data = NULL;

      else
      {
         png_ptr->unknown_chunk.data = (png_bytep)png_malloc(png_ptr,
            (png_size_t)length);
         png_crc_read(png_ptr, (png_bytep)png_ptr->unknown_chunk.data, length);
      }

#ifdef PNG_READ_USER_CHUNKS_SUPPORTED
      if (png_ptr->read_user_chunk_fn != NULL)
      {
         /* Callback to user unknown chunk handler */
         int ret;
         ret = (*(png_ptr->read_user_chunk_fn))
           (png_ptr, &png_ptr->unknown_chunk);

         if (ret < 0)
            png_chunk_error(png_ptr, "error in user chunk");

         if (ret == 0)
         {
            if (!(png_ptr->chunk_name[0] & 0x20))
               if (png_handle_as_unknown(png_ptr, png_ptr->chunk_name) !=
                    PNG_HANDLE_CHUNK_ALWAYS)
                  png_chunk_error(png_ptr, "unknown critical chunk");
            png_set_unknown_chunks(png_ptr, info_ptr,
               &png_ptr->unknown_chunk, 1);
         }
      }

      else
#endif
        png_set_unknown_chunks(png_ptr, info_ptr, &png_ptr->unknown_chunk, 1);
      png_free(png_ptr, png_ptr->unknown_chunk.data);
      png_ptr->unknown_chunk.data = NULL;
   }

   else
#endif
      skip=length;
   png_push_crc_skip(png_ptr, skip);
}

void /* PRIVATE */
png_push_have_info(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr->info_fn != NULL)
      (*(png_ptr->info_fn))(png_ptr, info_ptr);
}

void /* PRIVATE */
png_push_have_end(png_structp png_ptr, png_infop info_ptr)
{
   if (png_ptr->end_fn != NULL)
      (*(png_ptr->end_fn))(png_ptr, info_ptr);
}

void /* PRIVATE */
png_push_have_row(png_structp png_ptr, png_bytep row)
{
   if (png_ptr->row_fn != NULL)
      (*(png_ptr->row_fn))(png_ptr, row, png_ptr->row_number,
         (int)png_ptr->pass);
}

void PNGAPI
png_progressive_combine_row(png_structp png_ptr,
   png_bytep old_row, png_bytep new_row)
{
   PNG_CONST int FARDATA png_pass_dsp_mask[7] =
      {0xff, 0x0f, 0xff, 0x33, 0xff, 0x55, 0xff};

   if (png_ptr == NULL)
      return;

   if (new_row != NULL)    /* new_row must == png_ptr->row_buf here. */
      png_combine_row(png_ptr, old_row, png_pass_dsp_mask[png_ptr->pass]);
}

void PNGAPI
png_set_progressive_read_fn(png_structp png_ptr, png_voidp progressive_ptr,
   png_progressive_info_ptr info_fn, png_progressive_row_ptr row_fn,
   png_progressive_end_ptr end_fn)
{
   if (png_ptr == NULL)
      return;

   png_ptr->info_fn = info_fn;
   png_ptr->row_fn = row_fn;
   png_ptr->end_fn = end_fn;

   png_set_read_fn(png_ptr, progressive_ptr, png_push_fill_buffer);
}

png_voidp PNGAPI
png_get_progressive_ptr(png_structp png_ptr)
{
   if (png_ptr == NULL)
      return (NULL);

   return png_ptr->io_ptr;
}
#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */


code:
/* pngpriv.h - private declarations for use inside libpng
 *
 * libpng version 1.4.5 - December 9, 2010
 * For conditions of distribution and use, see copyright notice in png.h
 * Copyright (c) 1998-2010 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
 */

/* The symbols declared in this file (including the functions declared
 * as PNG_EXTERN) are PRIVATE.  They are not part of the libpng public
 * interface, and are not recommended for use by regular applications.
 * Some of them may become public in the future; others may stay private,
 * change in an incompatible way, or even disappear.
 * Although the libpng users are not forbidden to include this header,
 * they should be well aware of the issues that may arise from doing so.
 */

#ifndef PNGPRIV_H
#define PNGPRIV_H

#ifndef PNG_VERSION_INFO_ONLY

#include <stdlib.h>

#ifndef PNG_EXTERN
/* The functions exported by PNG_EXTERN are internal functions, which
 * aren't usually used outside the library (as far as I know), so it is
 * debatable if they should be exported at all.  In the future, when it
 * is possible to have run-time registry of chunk-handling functions,
 * some of these will be made available again.
#  define PNG_EXTERN extern
 */
#  define PNG_EXTERN
#endif

/* Other defines specific to compilers can go here.  Try to keep
 * them inside an appropriate ifdef/endif pair for portability.
 */

#ifdef PNG_FLOATING_POINT_SUPPORTED
#  ifdef MACOS
     /* We need to check that <math.h> hasn't already been included earlier
      * as it seems it doesn't agree with <fp.h>, yet we should really use
      * <fp.h> if possible.
      */
#    if !defined(__MATH_H__) && !defined(__MATH_H) && !defined(__cmath__)
#      include <fp.h>
#    endif
#  else
#    include <math.h>
#  endif
#  if defined(_AMIGA) && defined(__SASC) && defined(_M68881)
     /* Amiga SAS/C: We must include builtin FPU functions when compiling using
      * MATH=68881
      */
#    include <m68881.h>
#  endif
#endif

/* Codewarrior on NT has linking problems without this. */
#if (defined(__MWERKS__) && defined(WIN32)) || defined(__STDC__)
#  define PNG_ALWAYS_EXTERN
#endif

/* This provides the non-ANSI (far) memory allocation routines. */
#if defined(__TURBOC__) && defined(__MSDOS__)
#  include <mem.h>
#  include <alloc.h>
#endif

#ifndef SHP
#if defined(WIN32) || defined(_Windows) || defined(_WINDOWS) || \
    defined(_WIN32) || defined(__WIN32__)
#  include <windows.h>  /* defines _WINDOWS_ macro */
#endif
#endif
/* Various modes of operation.  Note that after an init, mode is set to
 * zero automatically when the structure is created.
 */
#define PNG_HAVE_IHDR               0x01
#define PNG_HAVE_PLTE               0x02
#define PNG_HAVE_IDAT               0x04
#define PNG_AFTER_IDAT              0x08 /* Have complete zlib datastream */
#define PNG_HAVE_IEND               0x10
#define PNG_HAVE_gAMA               0x20
#define PNG_HAVE_cHRM               0x40
#define PNG_HAVE_sRGB               0x80
#define PNG_HAVE_CHUNK_HEADER      0x100
#define PNG_WROTE_tIME             0x200
#define PNG_WROTE_INFO_BEFORE_PLTE 0x400
#define PNG_BACKGROUND_IS_GRAY     0x800
#define PNG_HAVE_PNG_SIGNATURE    0x1000
#define PNG_HAVE_CHUNK_AFTER_IDAT 0x2000 /* Have another chunk after IDAT */

/* Flags for the transformations the PNG library does on the image data */
#define PNG_BGR                 0x0001
#define PNG_INTERLACE           0x0002
#define PNG_PACK                0x0004
#define PNG_SHIFT               0x0008
#define PNG_SWAP_BYTES          0x0010
#define PNG_INVERT_MONO         0x0020
#define PNG_QUANTIZE            0x0040 /* formerly PNG_DITHER */
#define PNG_BACKGROUND          0x0080
#define PNG_BACKGROUND_EXPAND   0x0100
                          /*    0x0200 unused */
#define PNG_16_TO_8             0x0400
#define PNG_RGBA                0x0800
#define PNG_EXPAND              0x1000
#define PNG_GAMMA               0x2000
#define PNG_GRAY_TO_RGB         0x4000
#define PNG_FILLER              0x8000L
#define PNG_PACKSWAP           0x10000L
#define PNG_SWAP_ALPHA         0x20000L
#define PNG_STRIP_ALPHA        0x40000L
#define PNG_INVERT_ALPHA       0x80000L
#define PNG_USER_TRANSFORM    0x100000L
#define PNG_RGB_TO_GRAY_ERR   0x200000L
#define PNG_RGB_TO_GRAY_WARN  0x400000L
#define PNG_RGB_TO_GRAY       0x600000L  /* two bits, RGB_TO_GRAY_ERR|WARN */
                       /*     0x800000L     Unused */
#define PNG_ADD_ALPHA         0x1000000L  /* Added to libpng-1.2.7 */
#define PNG_EXPAND_tRNS       0x2000000L  /* Added to libpng-1.2.9 */
                       /*   0x4000000L  unused */
                       /*   0x8000000L  unused */
                       /*  0x10000000L  unused */
                       /*  0x20000000L  unused */
                       /*  0x40000000L  unused */

/* Flags for png_create_struct */
#define PNG_STRUCT_PNG   0x0001
#define PNG_STRUCT_INFO  0x0002

/* Scaling factor for filter heuristic weighting calculations */
#define PNG_WEIGHT_SHIFT 8
#define PNG_WEIGHT_FACTOR (1<<(PNG_WEIGHT_SHIFT))
#define PNG_COST_SHIFT 3
#define PNG_COST_FACTOR (1<<(PNG_COST_SHIFT))

/* Flags for the png_ptr->flags rather than declaring a byte for each one */
#define PNG_FLAG_ZLIB_CUSTOM_STRATEGY     0x0001
#define PNG_FLAG_ZLIB_CUSTOM_LEVEL        0x0002
#define PNG_FLAG_ZLIB_CUSTOM_MEM_LEVEL    0x0004
#define PNG_FLAG_ZLIB_CUSTOM_WINDOW_BITS  0x0008
#define PNG_FLAG_ZLIB_CUSTOM_METHOD       0x0010
#define PNG_FLAG_ZLIB_FINISHED            0x0020
#define PNG_FLAG_ROW_INIT                 0x0040
#define PNG_FLAG_FILLER_AFTER             0x0080
#define PNG_FLAG_CRC_ANCILLARY_USE        0x0100
#define PNG_FLAG_CRC_ANCILLARY_NOWARN     0x0200
#define PNG_FLAG_CRC_CRITICAL_USE         0x0400
#define PNG_FLAG_CRC_CRITICAL_IGNORE      0x0800
                                /*        0x1000  unused */
                                /*        0x2000  unused */
                                /*        0x4000  unused */
#define PNG_FLAG_KEEP_UNKNOWN_CHUNKS      0x8000L
#define PNG_FLAG_KEEP_UNSAFE_CHUNKS       0x10000L
#define PNG_FLAG_LIBRARY_MISMATCH         0x20000L
#define PNG_FLAG_STRIP_ERROR_NUMBERS      0x40000L
#define PNG_FLAG_STRIP_ERROR_TEXT         0x80000L
#define PNG_FLAG_MALLOC_NULL_MEM_OK       0x100000L
#define PNG_FLAG_ADD_ALPHA                0x200000L  /* Added to libpng-1.2.8 */
#define PNG_FLAG_STRIP_ALPHA              0x400000L  /* Added to libpng-1.2.8 */
#define PNG_FLAG_BENIGN_ERRORS_WARN       0x800000L  /* Added to libpng-1.4.0 */
                                  /*     0x1000000L  unused */
                                  /*     0x2000000L  unused */
                                  /*     0x4000000L  unused */
                                  /*     0x8000000L  unused */
                                  /*    0x10000000L  unused */
                                  /*    0x20000000L  unused */
                                  /*    0x40000000L  unused */

#define PNG_FLAG_CRC_ANCILLARY_MASK (PNG_FLAG_CRC_ANCILLARY_USE | \
                                     PNG_FLAG_CRC_ANCILLARY_NOWARN)

#define PNG_FLAG_CRC_CRITICAL_MASK  (PNG_FLAG_CRC_CRITICAL_USE | \
                                     PNG_FLAG_CRC_CRITICAL_IGNORE)

#define PNG_FLAG_CRC_MASK           (PNG_FLAG_CRC_ANCILLARY_MASK | \
                                     PNG_FLAG_CRC_CRITICAL_MASK)

/* Save typing and make code easier to understand */

#define PNG_COLOR_DIST(c1, c2) (abs((int)((c1).red) - (int)((c2).red)) + \
   abs((int)((c1).green) - (int)((c2).green)) + \
   abs((int)((c1).blue) - (int)((c2).blue)))

/* Added to libpng-1.2.6 JB */
#define PNG_ROWBYTES(pixel_bits, width) \
    ((pixel_bits) >= 8 ? \
    ((png_size_t)(width) * (((png_size_t)(pixel_bits)) >> 3)) : \
    (( ((png_size_t)(width) * ((png_size_t)(pixel_bits))) + 7) >> 3) )

/* PNG_OUT_OF_RANGE returns true if value is outside the range
 * ideal-delta..ideal+delta.  Each argument is evaluated twice.
 * "ideal" and "delta" should be constants, normally simple
 * integers, "value" a variable. Added to libpng-1.2.6 JB
 */
#define PNG_OUT_OF_RANGE(value, ideal, delta) \
        ( (value) < (ideal)-(delta) || (value) > (ideal)+(delta) )

/* Constant strings for known chunk types.  If you need to add a chunk,
 * define the name here, and add an invocation of the macro wherever it's
 * needed.
 */
#define PNG_IHDR PNG_CONST png_byte png_IHDR[5] = { 73,  72,  68,  82, '\0'}
#define PNG_IDAT PNG_CONST png_byte png_IDAT[5] = { 73,  68,  65,  84, '\0'}
#define PNG_IEND PNG_CONST png_byte png_IEND[5] = { 73,  69,  78,  68, '\0'}
#define PNG_PLTE PNG_CONST png_byte png_PLTE[5] = { 80,  76,  84,  69, '\0'}
#define PNG_bKGD PNG_CONST png_byte png_bKGD[5] = { 98,  75,  71,  68, '\0'}
#define PNG_cHRM PNG_CONST png_byte png_cHRM[5] = { 99,  72,  82,  77, '\0'}
#define PNG_gAMA PNG_CONST png_byte png_gAMA[5] = {103,  65,  77,  65, '\0'}
#define PNG_hIST PNG_CONST png_byte png_hIST[5] = {104,  73,  83,  84, '\0'}
#define PNG_iCCP PNG_CONST png_byte png_iCCP[5] = {105,  67,  67,  80, '\0'}
#define PNG_iTXt PNG_CONST png_byte png_iTXt[5] = {105,  84,  88, 116, '\0'}
#define PNG_oFFs PNG_CONST png_byte png_oFFs[5] = {111,  70,  70, 115, '\0'}
#define PNG_pCAL PNG_CONST png_byte png_pCAL[5] = {112,  67,  65,  76, '\0'}
#define PNG_sCAL PNG_CONST png_byte png_sCAL[5] = {115,  67,  65,  76, '\0'}
#define PNG_pHYs PNG_CONST png_byte png_pHYs[5] = {112,  72,  89, 115, '\0'}
#define PNG_sBIT PNG_CONST png_byte png_sBIT[5] = {115,  66,  73,  84, '\0'}
#define PNG_sPLT PNG_CONST png_byte png_sPLT[5] = {115,  80,  76,  84, '\0'}
#define PNG_sRGB PNG_CONST png_byte png_sRGB[5] = {115,  82,  71,  66, '\0'}
#define PNG_sTER PNG_CONST png_byte png_sTER[5] = {115,  84,  69,  82, '\0'}
#define PNG_tEXt PNG_CONST png_byte png_tEXt[5] = {116,  69,  88, 116, '\0'}
#define PNG_tIME PNG_CONST png_byte png_tIME[5] = {116,  73,  77,  69, '\0'}
#define PNG_tRNS PNG_CONST png_byte png_tRNS[5] = {116,  82,  78,  83, '\0'}
#define PNG_zTXt PNG_CONST png_byte png_zTXt[5] = {122,  84,  88, 116, '\0'}

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

/* These functions are used internally in the code.  They generally
 * shouldn't be used unless you are writing code to add or replace some
 * functionality in libpng.  More information about most functions can
 * be found in the files where the functions are located.
 */

/* Allocate memory for an internal libpng struct */
PNG_EXTERN png_voidp png_create_struct PNGARG((int type));

/* Free memory from internal libpng struct */
PNG_EXTERN void png_destroy_struct PNGARG((png_voidp struct_ptr));

PNG_EXTERN png_voidp png_create_struct_2 PNGARG((int type, png_malloc_ptr
  malloc_fn, png_voidp mem_ptr));
PNG_EXTERN void png_destroy_struct_2 PNGARG((png_voidp struct_ptr,
   png_free_ptr free_fn, png_voidp mem_ptr));

/* Free any memory that info_ptr points to and reset struct. */
PNG_EXTERN void png_info_destroy PNGARG((png_structp png_ptr,
   png_infop info_ptr));

/* Function to allocate memory for zlib.  PNGAPI is disallowed. */
PNG_EXTERN voidpf png_zalloc PNGARG((voidpf png_ptr, uInt items, uInt size));

/* Function to free memory for zlib.  PNGAPI is disallowed. */
PNG_EXTERN void png_zfree PNGARG((voidpf png_ptr, voidpf ptr));

/* Next four functions are used internally as callbacks.  PNGAPI is required
 * but not PNG_EXPORT.  PNGAPI added at libpng version 1.2.3. */

PNG_EXTERN void PNGAPI png_default_read_data PNGARG((png_structp png_ptr,
   png_bytep data, png_size_t length));

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_EXTERN void PNGAPI png_push_fill_buffer PNGARG((png_structp png_ptr,
   png_bytep buffer, png_size_t length));
#endif

PNG_EXTERN void PNGAPI png_default_write_data PNGARG((png_structp png_ptr,
   png_bytep data, png_size_t length));

#ifdef PNG_WRITE_FLUSH_SUPPORTED
#ifdef PNG_STDIO_SUPPORTED
PNG_EXTERN void PNGAPI png_default_flush PNGARG((png_structp png_ptr));
#endif
#endif

/* Reset the CRC variable */
PNG_EXTERN void png_reset_crc PNGARG((png_structp png_ptr));

/* Write the "data" buffer to whatever output you are using */
PNG_EXTERN void png_write_data PNGARG((png_structp png_ptr, png_bytep data,
   png_size_t length));

/* Read and check the PNG file signature */
PNG_EXTERN void png_read_sig PNGARG((png_structp png_ptr, png_infop info_ptr));

/* Read the chunk header (length + type name) */
PNG_EXTERN png_uint_32 png_read_chunk_header PNGARG((png_structp png_ptr));

/* Read data from whatever input you are using into the "data" buffer */
PNG_EXTERN void png_read_data PNGARG((png_structp png_ptr, png_bytep data,
   png_size_t length));

/* Read bytes into buf, and update png_ptr->crc */
PNG_EXTERN void png_crc_read PNGARG((png_structp png_ptr, png_bytep buf,
   png_size_t length));

/* Decompress data in a chunk that uses compression */
#if defined(PNG_zTXt_SUPPORTED) || defined(PNG_iTXt_SUPPORTED) || \
    defined(PNG_iCCP_SUPPORTED) || defined(PNG_sPLT_SUPPORTED)
PNG_EXTERN void png_decompress_chunk PNGARG((png_structp png_ptr,
   int comp_type, png_size_t chunklength, png_size_t prefix_length,
   png_size_t *data_length));
#endif

/* Read "skip" bytes, read the file crc, and (optionally) verify png_ptr->crc */
PNG_EXTERN int png_crc_finish PNGARG((png_structp png_ptr, png_uint_32 skip));

/* Read the CRC from the file and compare it to the libpng calculated CRC */
PNG_EXTERN int png_crc_error PNGARG((png_structp png_ptr));

/* Calculate the CRC over a section of data.  Note that we are only
 * passing a maximum of 64K on systems that have this as a memory limit,
 * since this is the maximum buffer size we can specify.
 */
PNG_EXTERN void png_calculate_crc PNGARG((png_structp png_ptr, png_bytep ptr,
   png_size_t length));

#ifdef PNG_WRITE_FLUSH_SUPPORTED
PNG_EXTERN void png_flush PNGARG((png_structp png_ptr));
#endif

/* Write various chunks */

/* Write the IHDR chunk, and update the png_struct with the necessary
 * information.
 */
PNG_EXTERN void png_write_IHDR PNGARG((png_structp png_ptr, png_uint_32 width,
   png_uint_32 height,
   int bit_depth, int color_type, int compression_method, int filter_method,
   int interlace_method));

PNG_EXTERN void png_write_PLTE PNGARG((png_structp png_ptr, png_colorp palette,
   png_uint_32 num_pal));

PNG_EXTERN void png_write_IDAT PNGARG((png_structp png_ptr, png_bytep data,
   png_size_t length));

PNG_EXTERN void png_write_IEND PNGARG((png_structp png_ptr));

#ifdef PNG_WRITE_gAMA_SUPPORTED
#ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_EXTERN void png_write_gAMA PNGARG((png_structp png_ptr, double file_gamma));
#endif
#ifdef PNG_FIXED_POINT_SUPPORTED
PNG_EXTERN void png_write_gAMA_fixed PNGARG((png_structp png_ptr,
    png_fixed_point file_gamma));
#endif
#endif

#ifdef PNG_WRITE_sBIT_SUPPORTED
PNG_EXTERN void png_write_sBIT PNGARG((png_structp png_ptr, png_color_8p sbit,
   int color_type));
#endif

#ifdef PNG_WRITE_cHRM_SUPPORTED
#ifdef PNG_FLOATING_POINT_SUPPORTED
PNG_EXTERN void png_write_cHRM PNGARG((png_structp png_ptr,
   double white_x, double white_y,
   double red_x, double red_y, double green_x, double green_y,
   double blue_x, double blue_y));
#endif
PNG_EXTERN void png_write_cHRM_fixed PNGARG((png_structp png_ptr,
   png_fixed_point int_white_x, png_fixed_point int_white_y,
   png_fixed_point int_red_x, png_fixed_point int_red_y, png_fixed_point
   int_green_x, png_fixed_point int_green_y, png_fixed_point int_blue_x,
   png_fixed_point int_blue_y));
#endif

#ifdef PNG_WRITE_sRGB_SUPPORTED
PNG_EXTERN void png_write_sRGB PNGARG((png_structp png_ptr,
   int intent));
#endif

#ifdef PNG_WRITE_iCCP_SUPPORTED
PNG_EXTERN void png_write_iCCP PNGARG((png_structp png_ptr,
   png_charp name, int compression_type,
   png_charp profile, int proflen));
   /* Note to maintainer: profile should be png_bytep */
#endif

#ifdef PNG_WRITE_sPLT_SUPPORTED
PNG_EXTERN void png_write_sPLT PNGARG((png_structp png_ptr,
   png_sPLT_tp palette));
#endif

#ifdef PNG_WRITE_tRNS_SUPPORTED
PNG_EXTERN void png_write_tRNS PNGARG((png_structp png_ptr, png_bytep trans,
   png_color_16p values, int number, int color_type));
#endif

#ifdef PNG_WRITE_bKGD_SUPPORTED
PNG_EXTERN void png_write_bKGD PNGARG((png_structp png_ptr,
   png_color_16p values, int color_type));
#endif

#ifdef PNG_WRITE_hIST_SUPPORTED
PNG_EXTERN void png_write_hIST PNGARG((png_structp png_ptr, png_uint_16p hist,
   int num_hist));
#endif

#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_pCAL_SUPPORTED) || \
    defined(PNG_WRITE_iCCP_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
PNG_EXTERN png_size_t png_check_keyword PNGARG((png_structp png_ptr,
   png_charp key, png_charpp new_key));
#endif

#ifdef PNG_WRITE_tEXt_SUPPORTED
PNG_EXTERN void png_write_tEXt PNGARG((png_structp png_ptr, png_charp key,
   png_charp text, png_size_t text_len));
#endif

#ifdef PNG_WRITE_zTXt_SUPPORTED
PNG_EXTERN void png_write_zTXt PNGARG((png_structp png_ptr, png_charp key,
   png_charp text, png_size_t text_len, int compression));
#endif

#ifdef PNG_WRITE_iTXt_SUPPORTED
PNG_EXTERN void png_write_iTXt PNGARG((png_structp png_ptr,
   int compression, png_charp key, png_charp lang, png_charp lang_key,
   png_charp text));
#endif

#ifdef PNG_TEXT_SUPPORTED  /* Added at version 1.0.14 and 1.2.4 */
PNG_EXTERN int png_set_text_2 PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_textp text_ptr, int num_text));
#endif

#ifdef PNG_WRITE_oFFs_SUPPORTED
PNG_EXTERN void png_write_oFFs PNGARG((png_structp png_ptr,
   png_int_32 x_offset, png_int_32 y_offset, int unit_type));
#endif

#ifdef PNG_WRITE_pCAL_SUPPORTED
PNG_EXTERN void png_write_pCAL PNGARG((png_structp png_ptr, png_charp purpose,
   png_int_32 X0, png_int_32 X1, int type, int nparams,
   png_charp units, png_charpp params));
#endif

#ifdef PNG_WRITE_pHYs_SUPPORTED
PNG_EXTERN void png_write_pHYs PNGARG((png_structp png_ptr,
   png_uint_32 x_pixels_per_unit, png_uint_32 y_pixels_per_unit,
   int unit_type));
#endif

#ifdef PNG_WRITE_tIME_SUPPORTED
PNG_EXTERN void png_write_tIME PNGARG((png_structp png_ptr,
   png_timep mod_time));
#endif

#ifdef PNG_WRITE_sCAL_SUPPORTED
#if defined(PNG_FLOATING_POINT_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)
PNG_EXTERN void png_write_sCAL PNGARG((png_structp png_ptr,
   int unit, double width, double height));
#else
#ifdef PNG_FIXED_POINT_SUPPORTED
PNG_EXTERN void png_write_sCAL_s PNGARG((png_structp png_ptr,
   int unit, png_charp width, png_charp height));
#endif
#endif
#endif

/* Called when finished processing a row of data */
PNG_EXTERN void png_write_finish_row PNGARG((png_structp png_ptr));

/* Internal use only.   Called before first row of data */
PNG_EXTERN void png_write_start_row PNGARG((png_structp png_ptr));

#ifdef PNG_READ_GAMMA_SUPPORTED
PNG_EXTERN void png_build_gamma_table PNGARG((png_structp png_ptr,
   png_byte bit_depth));
#endif

/* Combine a row of data, dealing with alpha, etc. if requested */
PNG_EXTERN void png_combine_row PNGARG((png_structp png_ptr, png_bytep row,
   int mask));

#ifdef PNG_READ_INTERLACING_SUPPORTED
/* Expand an interlaced row */
/* OLD pre-1.0.9 interface:
PNG_EXTERN void png_do_read_interlace PNGARG((png_row_infop row_info,
   png_bytep row, int pass, png_uint_32 transformations));
 */
PNG_EXTERN void png_do_read_interlace PNGARG((png_structp png_ptr));
#endif

/* GRR TO DO (2.0 or whenever):  simplify other internal calling interfaces */

#ifdef PNG_WRITE_INTERLACING_SUPPORTED
/* Grab pixels out of a row for an interlaced pass */
PNG_EXTERN void png_do_write_interlace PNGARG((png_row_infop row_info,
   png_bytep row, int pass));
#endif

/* Unfilter a row */
PNG_EXTERN void png_read_filter_row PNGARG((png_structp png_ptr,
   png_row_infop row_info, png_bytep row, png_bytep prev_row, int filter));

/* Choose the best filter to use and filter the row data */
PNG_EXTERN void png_write_find_filter PNGARG((png_structp png_ptr,
   png_row_infop row_info));

/* Write out the filtered row. */
PNG_EXTERN void png_write_filtered_row PNGARG((png_structp png_ptr,
   png_bytep filtered_row));
/* Finish a row while reading, dealing with interlacing passes, etc. */
PNG_EXTERN void png_read_finish_row PNGARG((png_structp png_ptr));

/* Initialize the row buffers, etc. */
PNG_EXTERN void png_read_start_row PNGARG((png_structp png_ptr));
/* Optional call to update the users info structure */
PNG_EXTERN void png_read_transform_info PNGARG((png_structp png_ptr,
   png_infop info_ptr));

/* These are the functions that do the transformations */
#ifdef PNG_READ_FILLER_SUPPORTED
PNG_EXTERN void png_do_read_filler PNGARG((png_row_infop row_info,
   png_bytep row, png_uint_32 filler, png_uint_32 flags));
#endif

#ifdef PNG_READ_SWAP_ALPHA_SUPPORTED
PNG_EXTERN void png_do_read_swap_alpha PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
PNG_EXTERN void png_do_write_swap_alpha PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

#ifdef PNG_READ_INVERT_ALPHA_SUPPORTED
PNG_EXTERN void png_do_read_invert_alpha PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
PNG_EXTERN void png_do_write_invert_alpha PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

#if defined(PNG_WRITE_FILLER_SUPPORTED) || \
    defined(PNG_READ_STRIP_ALPHA_SUPPORTED)
PNG_EXTERN void png_do_strip_filler PNGARG((png_row_infop row_info,
   png_bytep row, png_uint_32 flags));
#endif

#if defined(PNG_READ_SWAP_SUPPORTED) || defined(PNG_WRITE_SWAP_SUPPORTED)
PNG_EXTERN void png_do_swap PNGARG((png_row_infop row_info, png_bytep row));
#endif

#if defined(PNG_READ_PACKSWAP_SUPPORTED) || \
    defined(PNG_WRITE_PACKSWAP_SUPPORTED)
PNG_EXTERN void png_do_packswap PNGARG((png_row_infop row_info, png_bytep row));
#endif

#ifdef PNG_READ_RGB_TO_GRAY_SUPPORTED
PNG_EXTERN int png_do_rgb_to_gray PNGARG((png_structp png_ptr, png_row_infop
   row_info, png_bytep row));
#endif

#ifdef PNG_READ_GRAY_TO_RGB_SUPPORTED
PNG_EXTERN void png_do_gray_to_rgb PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

#ifdef PNG_READ_PACK_SUPPORTED
PNG_EXTERN void png_do_unpack PNGARG((png_row_infop row_info, png_bytep row));
#endif

#ifdef PNG_READ_SHIFT_SUPPORTED
PNG_EXTERN void png_do_unshift PNGARG((png_row_infop row_info, png_bytep row,
   png_color_8p sig_bits));
#endif

#if defined(PNG_READ_INVERT_SUPPORTED) || defined(PNG_WRITE_INVERT_SUPPORTED)
PNG_EXTERN void png_do_invert PNGARG((png_row_infop row_info, png_bytep row));
#endif

#ifdef PNG_READ_16_TO_8_SUPPORTED
PNG_EXTERN void png_do_chop PNGARG((png_row_infop row_info, png_bytep row));
#endif

#ifdef PNG_READ_QUANTIZE_SUPPORTED
PNG_EXTERN void png_do_quantize PNGARG((png_row_infop row_info,
   png_bytep row, png_bytep palette_lookup, png_bytep quantize_lookup));

#  ifdef PNG_CORRECT_PALETTE_SUPPORTED
PNG_EXTERN void png_correct_palette PNGARG((png_structp png_ptr,
   png_colorp palette, int num_palette));
#  endif
#endif

#if defined(PNG_READ_BGR_SUPPORTED) || defined(PNG_WRITE_BGR_SUPPORTED)
PNG_EXTERN void png_do_bgr PNGARG((png_row_infop row_info, png_bytep row));
#endif

#ifdef PNG_WRITE_PACK_SUPPORTED
PNG_EXTERN void png_do_pack PNGARG((png_row_infop row_info,
   png_bytep row, png_uint_32 bit_depth));
#endif

#ifdef PNG_WRITE_SHIFT_SUPPORTED
PNG_EXTERN void png_do_shift PNGARG((png_row_infop row_info, png_bytep row,
   png_color_8p bit_depth));
#endif

#ifdef PNG_READ_BACKGROUND_SUPPORTED
#ifdef PNG_READ_GAMMA_SUPPORTED
PNG_EXTERN void png_do_background PNGARG((png_row_infop row_info, png_bytep row,
   png_color_16p trans_color, png_color_16p background,
   png_color_16p background_1,
   png_bytep gamma_table, png_bytep gamma_from_1, png_bytep gamma_to_1,
   png_uint_16pp gamma_16, png_uint_16pp gamma_16_from_1,
   png_uint_16pp gamma_16_to_1, int gamma_shift));
#else
PNG_EXTERN void png_do_background PNGARG((png_row_infop row_info, png_bytep row,
   png_color_16p trans_color, png_color_16p background));
#endif
#endif

#ifdef PNG_READ_GAMMA_SUPPORTED
PNG_EXTERN void png_do_gamma PNGARG((png_row_infop row_info, png_bytep row,
   png_bytep gamma_table, png_uint_16pp gamma_16_table,
   int gamma_shift));
#endif

#ifdef PNG_READ_EXPAND_SUPPORTED
PNG_EXTERN void png_do_expand_palette PNGARG((png_row_infop row_info,
   png_bytep row, png_colorp palette, png_bytep trans, int num_trans));
PNG_EXTERN void png_do_expand PNGARG((png_row_infop row_info,
   png_bytep row, png_color_16p trans_value));
#endif

/* The following decodes the appropriate chunks, and does error correction,
 * then calls the appropriate callback for the chunk if it is valid.
 */

/* Decode the IHDR chunk */
PNG_EXTERN void png_handle_IHDR PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
PNG_EXTERN void png_handle_PLTE PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
PNG_EXTERN void png_handle_IEND PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));

#ifdef PNG_READ_bKGD_SUPPORTED
PNG_EXTERN void png_handle_bKGD PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_cHRM_SUPPORTED
PNG_EXTERN void png_handle_cHRM PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_gAMA_SUPPORTED
PNG_EXTERN void png_handle_gAMA PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_hIST_SUPPORTED
PNG_EXTERN void png_handle_hIST PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_iCCP_SUPPORTED
PNG_EXTERN void png_handle_iCCP PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif /* PNG_READ_iCCP_SUPPORTED */

#ifdef PNG_READ_iTXt_SUPPORTED
PNG_EXTERN void png_handle_iTXt PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_oFFs_SUPPORTED
PNG_EXTERN void png_handle_oFFs PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_pCAL_SUPPORTED
PNG_EXTERN void png_handle_pCAL PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_pHYs_SUPPORTED
PNG_EXTERN void png_handle_pHYs PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_sBIT_SUPPORTED
PNG_EXTERN void png_handle_sBIT PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_sCAL_SUPPORTED
PNG_EXTERN void png_handle_sCAL PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_sPLT_SUPPORTED
PNG_EXTERN void png_handle_sPLT PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif /* PNG_READ_sPLT_SUPPORTED */

#ifdef PNG_READ_sRGB_SUPPORTED
PNG_EXTERN void png_handle_sRGB PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_tEXt_SUPPORTED
PNG_EXTERN void png_handle_tEXt PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_tIME_SUPPORTED
PNG_EXTERN void png_handle_tIME PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_tRNS_SUPPORTED
PNG_EXTERN void png_handle_tRNS PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

#ifdef PNG_READ_zTXt_SUPPORTED
PNG_EXTERN void png_handle_zTXt PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_uint_32 length));
#endif

PNG_EXTERN void png_handle_unknown PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_uint_32 length));

PNG_EXTERN void png_check_chunk_name PNGARG((png_structp png_ptr,
   png_bytep chunk_name));

/* Handle the transformations for reading and writing */
PNG_EXTERN void png_do_read_transformations PNGARG((png_structp png_ptr));
PNG_EXTERN void png_do_write_transformations PNGARG((png_structp png_ptr));

PNG_EXTERN void png_init_read_transformations PNGARG((png_structp png_ptr));

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED
PNG_EXTERN void png_push_read_chunk PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_push_read_sig PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_push_check_crc PNGARG((png_structp png_ptr));
PNG_EXTERN void png_push_crc_skip PNGARG((png_structp png_ptr,
   png_uint_32 length));
PNG_EXTERN void png_push_crc_finish PNGARG((png_structp png_ptr));
PNG_EXTERN void png_push_save_buffer PNGARG((png_structp png_ptr));
PNG_EXTERN void png_push_restore_buffer PNGARG((png_structp png_ptr,
   png_bytep buffer, png_size_t buffer_length));
PNG_EXTERN void png_push_read_IDAT PNGARG((png_structp png_ptr));
PNG_EXTERN void png_process_IDAT_data PNGARG((png_structp png_ptr,
   png_bytep buffer, png_size_t buffer_length));
PNG_EXTERN void png_push_process_row PNGARG((png_structp png_ptr));
PNG_EXTERN void png_push_handle_unknown PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_uint_32 length));
PNG_EXTERN void png_push_have_info PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_push_have_end PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_push_have_row PNGARG((png_structp png_ptr, png_bytep row));
PNG_EXTERN void png_push_read_end PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_process_some_data PNGARG((png_structp png_ptr,
   png_infop info_ptr));
PNG_EXTERN void png_read_push_finish_row PNGARG((png_structp png_ptr));
#ifdef PNG_READ_tEXt_SUPPORTED
PNG_EXTERN void png_push_handle_tEXt PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_uint_32 length));
PNG_EXTERN void png_push_read_tEXt PNGARG((png_structp png_ptr,
   png_infop info_ptr));
#endif
#ifdef PNG_READ_zTXt_SUPPORTED
PNG_EXTERN void png_push_handle_zTXt PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_uint_32 length));
PNG_EXTERN void png_push_read_zTXt PNGARG((png_structp png_ptr,
   png_infop info_ptr));
#endif
#ifdef PNG_READ_iTXt_SUPPORTED
PNG_EXTERN void png_push_handle_iTXt PNGARG((png_structp png_ptr,
   png_infop info_ptr, png_uint_32 length));
PNG_EXTERN void png_push_read_iTXt PNGARG((png_structp png_ptr,
   png_infop info_ptr));
#endif

#endif /* PNG_PROGRESSIVE_READ_SUPPORTED */

#ifdef PNG_MNG_FEATURES_SUPPORTED
PNG_EXTERN void png_do_read_intrapixel PNGARG((png_row_infop row_info,
   png_bytep row));
PNG_EXTERN void png_do_write_intrapixel PNGARG((png_row_infop row_info,
   png_bytep row));
#endif

/* Added at libpng version 1.4.0 */
#ifdef PNG_cHRM_SUPPORTED
PNG_EXTERN int png_check_cHRM_fixed PNGARG((png_structp png_ptr,
   png_fixed_point int_white_x, png_fixed_point int_white_y,
   png_fixed_point int_red_x, png_fixed_point int_red_y, png_fixed_point
   int_green_x, png_fixed_point int_green_y, png_fixed_point int_blue_x,
   png_fixed_point int_blue_y));
#endif

#ifdef PNG_cHRM_SUPPORTED
#ifdef PNG_CHECK_cHRM_SUPPORTED
/* Added at libpng version 1.2.34 and 1.4.0 */
PNG_EXTERN void png_64bit_product PNGARG((long v1, long v2,
   unsigned long *hi_product, unsigned long *lo_product));
#endif
#endif

/* Added at libpng version 1.4.0 */
PNG_EXTERN void png_check_IHDR PNGARG((png_structp png_ptr,
   png_uint_32 width, png_uint_32 height, int bit_depth,
   int color_type, int interlace_type, int compression_type,
   int filter_type));

/* Free all memory used by the read (old method - NOT DLL EXPORTED) */
PNG_EXTERN void png_read_destroy PNGARG((png_structp png_ptr, png_infop info_ptr,
   png_infop end_info_ptr));

/* Free any memory used in png_ptr struct (old method - NOT DLL EXPORTED) */
PNG_EXTERN void png_write_destroy PNGARG((png_structp png_ptr));

#ifdef USE_FAR_KEYWORD  /* memory model conversion function */
PNG_EXTERN void *png_far_to_near PNGARG((png_structp png_ptr,png_voidp ptr,
   int check));
#endif /* USE_FAR_KEYWORD */

/* Define PNG_DEBUG at compile time for debugging information.  Higher
 * numbers for PNG_DEBUG mean more debugging information.  This has
 * only been added since version 0.95 so it is not implemented throughout
 * libpng yet, but more support will be added as needed.
 */
#ifdef PNG_DEBUG
#if (PNG_DEBUG > 0)
#if !defined(PNG_DEBUG_FILE) && defined(_MSC_VER)
#include <crtdbg.h>
#if (PNG_DEBUG > 1)
#ifndef _DEBUG
#  define _DEBUG
#endif
#ifndef png_debug
#define png_debug(l,m)  _RPT0(_CRT_WARN,m PNG_STRING_NEWLINE)
#endif
#ifndef png_debug1
#define png_debug1(l,m,p1)  _RPT1(_CRT_WARN,m PNG_STRING_NEWLINE,p1)
#endif
#ifndef png_debug2
#define png_debug2(l,m,p1,p2) _RPT2(_CRT_WARN,m PNG_STRING_NEWLINE,p1,p2)
#endif
#endif
#else /* PNG_DEBUG_FILE || !_MSC_VER */
#ifndef PNG_DEBUG_FILE
#define PNG_DEBUG_FILE stderr
#endif /* PNG_DEBUG_FILE */

#if (PNG_DEBUG > 1)
/* Note: ["%s"m PNG_STRING_NEWLINE] probably does not work on
 * non-ISO compilers
 */
#  ifdef __STDC__
#    ifndef png_debug
#      define png_debug(l,m) \
       { \
       int num_tabs=l; \
       fprintf(PNG_DEBUG_FILE,"%s"m PNG_STRING_NEWLINE,(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":"")))); \
       }
#    endif
#    ifndef png_debug1
#      define png_debug1(l,m,p1) \
       { \
       int num_tabs=l; \
       fprintf(PNG_DEBUG_FILE,"%s"m PNG_STRING_NEWLINE,(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":""))),p1); \
       }
#    endif
#    ifndef png_debug2
#      define png_debug2(l,m,p1,p2) \
       { \
       int num_tabs=l; \
       fprintf(PNG_DEBUG_FILE,"%s"m PNG_STRING_NEWLINE,(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":""))),p1,p2); \
       }
#    endif
#  else /* __STDC __ */
#    ifndef png_debug
#      define png_debug(l,m) \
       { \
       int num_tabs=l; \
       char format[256]; \
       snprintf(format,256,"%s%s%s",(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":""))), \
         m,PNG_STRING_NEWLINE); \
       fprintf(PNG_DEBUG_FILE,format); \
       }
#    endif
#    ifndef png_debug1
#      define png_debug1(l,m,p1) \
       { \
       int num_tabs=l; \
       char format[256]; \
       snprintf(format,256,"%s%s%s",(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":""))), \
         m,PNG_STRING_NEWLINE); \
       fprintf(PNG_DEBUG_FILE,format,p1); \
       }
#    endif
#    ifndef png_debug2
#      define png_debug2(l,m,p1,p2) \
       { \
       int num_tabs=l; \
       char format[256]; \
       snprintf(format,256,"%s%s%s",(num_tabs==1 ? "\t" : \
         (num_tabs==2 ? "\t\t":(num_tabs>2 ? "\t\t\t":""))), \
         m,PNG_STRING_NEWLINE); \
       fprintf(PNG_DEBUG_FILE,format,p1,p2); \
       }
#    endif
#  endif /* __STDC __ */
#endif /* (PNG_DEBUG > 1) */

#endif /* _MSC_VER */
#endif /* (PNG_DEBUG > 0) */
#endif /* PNG_DEBUG */
#ifndef png_debug
#define png_debug(l, m)
#endif
#ifndef png_debug1
#define png_debug1(l, m, p1)
#endif
#ifndef png_debug2
#define png_debug2(l, m, p1, p2)
#endif

/* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */

#ifdef __cplusplus
}
#endif

#endif /* PNG_VERSION_INFO_ONLY */
#endif /* PNGPRIV_H */

license: mit