pngpread.c

一个国人自己实现图像库的程序（有参考价值）

/* pngpread.c - read a png file in push mode
 *
 * libpng 1.2.1 - December 12, 2001
 * For conditions of distribution and use, see copyright notice in png.h
 * Copyright (c) 1998-2001 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.)
 */

#define PNG_INTERNAL
#include "png.h"

#ifdef PNG_PROGRESSIVE_READ_SUPPORTED

/* 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)
{
   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)
{
   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;
      }
#if defined(PNG_READ_tEXt_SUPPORTED)
      case PNG_READ_tEXt_MODE:
      {
         png_push_read_tEXt(png_ptr, info_ptr);
         break;
      }
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
      case PNG_READ_zTXt_MODE:
      {
         png_push_read_zTXt(png_ptr, info_ptr);
         break;
      }
#endif
#if defined(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)
{
#ifdef PNG_USE_LOCAL_ARRAYS
      PNG_IHDR;
      PNG_IDAT;
      PNG_IEND;
      PNG_PLTE;
#if defined(PNG_READ_bKGD_SUPPORTED)
      PNG_bKGD;
#endif
#if defined(PNG_READ_cHRM_SUPPORTED)
      PNG_cHRM;
#endif
#if defined(PNG_READ_gAMA_SUPPORTED)
      PNG_gAMA;
#endif
#if defined(PNG_READ_hIST_SUPPORTED)
      PNG_hIST;
#endif
#if defined(PNG_READ_iCCP_SUPPORTED)
      PNG_iCCP;
#endif
#if defined(PNG_READ_iTXt_SUPPORTED)
      PNG_iTXt;
#endif
#if defined(PNG_READ_oFFs_SUPPORTED)
      PNG_oFFs;
#endif
#if defined(PNG_READ_pCAL_SUPPORTED)
      PNG_pCAL;
#endif
#if defined(PNG_READ_pHYs_SUPPORTED)
      PNG_pHYs;
#endif
#if defined(PNG_READ_sBIT_SUPPORTED)
      PNG_sBIT;
#endif
#if defined(PNG_READ_sCAL_SUPPORTED)
      PNG_sCAL;
#endif
#if defined(PNG_READ_sRGB_SUPPORTED)
      PNG_sRGB;
#endif
#if defined(PNG_READ_sPLT_SUPPORTED)
      PNG_sPLT;
#endif
#if defined(PNG_READ_tEXt_SUPPORTED)
      PNG_tEXt;
#endif
#if defined(PNG_READ_tIME_SUPPORTED)
      PNG_tIME;
#endif
#if defined(PNG_READ_tRNS_SUPPORTED)
      PNG_tRNS;
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
      PNG_zTXt;
#endif
#endif /* PNG_USE_LOCAL_ARRAYS */
   /* 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_32(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_IHDR, 4))
   {
      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_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_bytep)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_IDAT)
      {
         if (png_ptr->push_length == 0)
            return;

         if (png_ptr->mode & PNG_AFTER_IDAT)
            png_error(png_ptr, "Too many IDAT's 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_ptr->irowbytes;
      png_ptr->zstream.next_out = png_ptr->row_buf;
      return;
   }
   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);
   }
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(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
#if defined(PNG_READ_tEXt_SUPPORTED)
   else if (!png_memcmp(png_ptr->chunk_name, png_tEXt, 4))
   {
      png_push_handle_tEXt(png_ptr, info_ptr, png_ptr->push_length);
   }
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
   else if (!png_memcmp(png_ptr->chunk_name, png_zTXt, 4))
   {
      png_push_handle_zTXt(png_ptr, info_ptr, png_ptr->push_length);
   }
#endif
#if defined(PNG_READ_iTXt_SUPPORTED)
   else if (!png_memcmp(png_ptr->chunk_name, png_iTXt, 4))
   {
      png_push_handle_iTXt(png_ptr, info_ptr, png_ptr->push_length);
   }
#endif
   else
   {
      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);