pngread.c

一个国人自己实现图像库的程序（有参考价值）

/* pngread.c - read a PNG file
 *
 * 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.)
 *
 * This file contains routines that an application calls directly to
 * read a PNG file or stream.
 */

#define PNG_INTERNAL
#include "png.h"

/* Create a PNG structure for reading, and allocate any memory needed. */
png_structp PNGAPI
png_create_read_struct(png_const_charp user_png_ver, png_voidp error_ptr,
   png_error_ptr error_fn, png_error_ptr warn_fn)
{

#ifdef PNG_USER_MEM_SUPPORTED
   return (png_create_read_struct_2(user_png_ver, error_ptr, error_fn,
      warn_fn, png_voidp_NULL, png_malloc_ptr_NULL, png_free_ptr_NULL));
}

/* Alternate create PNG structure for reading, and allocate any memory needed. */
png_structp PNGAPI
png_create_read_struct_2(png_const_charp user_png_ver, png_voidp error_ptr,
   png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
   png_malloc_ptr malloc_fn, png_free_ptr free_fn)
{
#endif /* PNG_USER_MEM_SUPPORTED */

   png_structp png_ptr;

#ifdef PNG_SETJMP_SUPPORTED
#ifdef USE_FAR_KEYWORD
   jmp_buf jmpbuf;
#endif
#endif

   int i;

   png_debug(1, "in png_create_read_struct\n");
#ifdef PNG_USER_MEM_SUPPORTED
   if ((png_ptr = (png_structp)png_create_struct_2(PNG_STRUCT_PNG,
      (png_malloc_ptr)malloc_fn, (png_voidp)mem_ptr)) == NULL)
#else
   if ((png_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG)) == NULL)
#endif
      return (NULL);

#ifdef PNG_ASSEMBLER_CODE_SUPPORTED
   png_init_mmx_flags(png_ptr);   /* 1.2.0 addition */
#endif

#ifdef PNG_SETJMP_SUPPORTED
#ifdef USE_FAR_KEYWORD
   if (setjmp(jmpbuf))
#else
   if (setjmp(png_ptr->jmpbuf))
#endif
   {
      png_free(png_ptr, png_ptr->zbuf);
      png_ptr->zbuf=NULL;
      png_destroy_struct(png_ptr);
      return (NULL);
   }
#ifdef USE_FAR_KEYWORD
   png_memcpy(png_ptr->jmpbuf,jmpbuf,sizeof(jmp_buf));
#endif
#endif

#ifdef PNG_USER_MEM_SUPPORTED
   png_set_mem_fn(png_ptr, mem_ptr, malloc_fn, free_fn);
#endif

   png_set_error_fn(png_ptr, error_ptr, error_fn, warn_fn);

   i=0;
   do
   {
     if(user_png_ver[i] != png_libpng_ver[i])
        png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
   } while (png_libpng_ver[i++]);

   if (png_ptr->flags & PNG_FLAG_LIBRARY_MISMATCH)
   {
     /* Libpng 0.90 and later are binary incompatible with libpng 0.89, so
      * we must recompile any applications that use any older library version.
      * For versions after libpng 1.0, we will be compatible, so we need
      * only check the first digit.
      */
     if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0] ||
         (user_png_ver[0] == '1' && user_png_ver[2] != png_libpng_ver[2]) ||
         (user_png_ver[0] == '0' && user_png_ver[2] < '9'))
     {
#if !defined(PNG_NO_STDIO) && !defined(_WIN32_WCE)
        char msg[80];
        if (user_png_ver)
        {
          sprintf(msg, "Application was compiled with png.h from libpng-%.20s",
             user_png_ver);
          png_warning(png_ptr, msg);
        }
        sprintf(msg, "Application  is  running with png.c from libpng-%.20s",
           png_libpng_ver);
        png_warning(png_ptr, msg);
#endif
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
        png_ptr->flags=0;
#endif
        png_error(png_ptr,
           "Incompatible libpng version in application and library");
     }
   }

   /* initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = (png_bytep)png_malloc(png_ptr,
     (png_uint_32)png_ptr->zbuf_size);
   png_ptr->zstream.zalloc = png_zalloc;
   png_ptr->zstream.zfree = png_zfree;
   png_ptr->zstream.opaque = (voidpf)png_ptr;

   switch (inflateInit(&png_ptr->zstream))
   {
     case Z_OK: /* Do nothing */ break;
     case Z_MEM_ERROR:
     case Z_STREAM_ERROR: png_error(png_ptr, "zlib memory error"); break;
     case Z_VERSION_ERROR: png_error(png_ptr, "zlib version error"); break;
     default: png_error(png_ptr, "Unknown zlib error");
   }

   png_ptr->zstream.next_out = png_ptr->zbuf;
   png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;

   png_set_read_fn(png_ptr, png_voidp_NULL, png_rw_ptr_NULL);

   return (png_ptr);
}

/* Initialize PNG structure for reading, and allocate any memory needed.
   This interface is deprecated in favour of the png_create_read_struct(),
   and it will eventually disappear. */
#undef png_read_init
void PNGAPI
png_read_init(png_structp png_ptr)
{
   /* We only come here via pre-1.0.7-compiled applications */
   png_read_init_2(png_ptr, "1.0.6 or earlier", 0, 0);
}

#undef png_read_init_2
void PNGAPI
png_read_init_2(png_structp png_ptr, png_const_charp user_png_ver,
   png_size_t png_struct_size, png_size_t png_info_size)
{
   /* We only come here via pre-1.0.12-compiled applications */
#if !defined(PNG_NO_STDIO) && !defined(_WIN32_WCE)
   if(sizeof(png_struct) > png_struct_size || sizeof(png_info) > png_info_size)
   {
      char msg[80];
      png_ptr->warning_fn=NULL;
      if (user_png_ver)
      {
        sprintf(msg, "Application was compiled with png.h from libpng-%.20s",
           user_png_ver);
        png_warning(png_ptr, msg);
      }
      sprintf(msg, "Application  is  running with png.c from libpng-%.20s",
         png_libpng_ver);
      png_warning(png_ptr, msg);
   }
#endif
   if(sizeof(png_struct) > png_struct_size)
     {
       png_ptr->error_fn=NULL;
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
       png_ptr->flags=0;
#endif
       png_error(png_ptr,
       "The png struct allocated by the application for reading is too small.");
     }
   if(sizeof(png_info) > png_info_size)
     {
       png_ptr->error_fn=NULL;
#ifdef PNG_ERROR_NUMBERS_SUPPORTED
       png_ptr->flags=0;
#endif
       png_error(png_ptr,
         "The info struct allocated by application for reading is too small.");
     }
   png_read_init_3(&png_ptr, user_png_ver, png_struct_size);
}

void PNGAPI
png_read_init_3(png_structpp ptr_ptr, png_const_charp user_png_ver,
   png_size_t png_struct_size)
{
#ifdef PNG_SETJMP_SUPPORTED
   jmp_buf tmp_jmp;  /* to save current jump buffer */
#endif

   int i=0;

   png_structp png_ptr=*ptr_ptr;

   do
   {
     if(user_png_ver[i] != png_libpng_ver[i])
     {
#ifdef PNG_LEGACY_SUPPORTED
       png_ptr->flags |= PNG_FLAG_LIBRARY_MISMATCH;
#else
       png_ptr->warning_fn=NULL;
       png_warning(png_ptr,
        "Application uses deprecated png_read_init() and should be recompiled.");
       break;
#endif
     }
   } while (png_libpng_ver[i++]);

   png_debug(1, "in png_read_init_3\n");

#ifdef PNG_SETJMP_SUPPORTED
   /* save jump buffer and error functions */
   png_memcpy(tmp_jmp, png_ptr->jmpbuf, sizeof (jmp_buf));
#endif

   if(sizeof(png_struct) > png_struct_size)
     {
       png_destroy_struct(png_ptr);
       *ptr_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG);
       png_ptr = *ptr_ptr;
     }

   /* reset all variables to 0 */
   png_memset(png_ptr, 0, sizeof (png_struct));

#ifdef PNG_SETJMP_SUPPORTED
   /* restore jump buffer */
   png_memcpy(png_ptr->jmpbuf, tmp_jmp, sizeof (jmp_buf));
#endif

   /* initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = (png_bytep)png_malloc(png_ptr,
     (png_uint_32)png_ptr->zbuf_size);
   png_ptr->zstream.zalloc = png_zalloc;
   png_ptr->zstream.zfree = png_zfree;
   png_ptr->zstream.opaque = (voidpf)png_ptr;

   switch (inflateInit(&png_ptr->zstream))
   {
     case Z_OK: /* Do nothing */ break;
     case Z_MEM_ERROR:
     case Z_STREAM_ERROR: png_error(png_ptr, "zlib memory"); break;
     case Z_VERSION_ERROR: png_error(png_ptr, "zlib version"); break;
     default: png_error(png_ptr, "Unknown zlib error");
   }

   png_ptr->zstream.next_out = png_ptr->zbuf;
   png_ptr->zstream.avail_out = (uInt)png_ptr->zbuf_size;

   png_set_read_fn(png_ptr, png_voidp_NULL, png_rw_ptr_NULL);
}

/* Read the information before the actual image data.  This has been
 * changed in v0.90 to allow reading a file that already has the magic
 * bytes read from the stream.  You can tell libpng how many bytes have
 * been read from the beginning of the stream (up to the maximum of 8)
 * via png_set_sig_bytes(), and we will only check the remaining bytes
 * here.  The application can then have access to the signature bytes we
 * read if it is determined that this isn't a valid PNG file.
 */
void PNGAPI
png_read_info(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_read_info\n");
   /* save jump buffer and error functions */
   /* If we haven't checked all of the PNG signature bytes, do so now. */
   if (png_ptr->sig_bytes < 8)
   {
      png_size_t num_checked = png_ptr->sig_bytes,
                 num_to_check = 8 - num_checked;

      png_read_data(png_ptr, &(info_ptr->signature[num_checked]), num_to_check);
      png_ptr->sig_bytes = 8;

      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");
      }
      if (num_checked < 3)
         png_ptr->mode |= PNG_HAVE_PNG_SIGNATURE;
   }

   for(;;)
   {
#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_sPLT_SUPPORTED)
      PNG_sPLT;
#endif
#if defined(PNG_READ_sRGB_SUPPORTED)
      PNG_sRGB;
#endif