pngread.c

一套图像处理程序,支持三种图像文件格式,我调试过了,很好用

/* pngread.c - read a png file

   libpng 1.0 beta 3 - version 0.89
   For conditions of distribution and use, see copyright notice in png.h
   Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
   May 25, 1996
   */

#define PNG_INTERNAL
#include "png.h"

/* Create a png structure for reading, and allocate any memory needed. */
png_structp
png_create_read_struct(png_const_charp user_png_ver, voidp error_ptr,
   png_error_ptr warn_fn, png_error_ptr error_fn)
{
   png_structp png_ptr;

   if ((png_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG)) == NULL)
   {
      return (png_structp)NULL;
   }

   if (setjmp(png_ptr->jmpbuf))
   {
      png_large_free(png_ptr, png_ptr->zbuf);
      png_free(png_ptr, png_ptr->zstream);
      png_destroy_struct(png_ptr);
      return (png_structp)NULL;
   }

   png_set_error_fn(png_ptr, error_ptr, warn_fn, error_fn);

   if (user_png_ver == NULL || strcmp(user_png_ver, png_libpng_ver))
   {
      if (user_png_ver == NULL || user_png_ver[0] != png_libpng_ver[0])
      {
         png_error(png_ptr, "Incompatible libpng versions");
      }
      else
      {
         png_warning(png_ptr, "Different libpng versions");
      }
   }

   /* initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = png_large_malloc(png_ptr, png_ptr->zbuf_size);

   png_ptr->zstream = (z_stream *)png_malloc(png_ptr, sizeof (z_stream));
   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, NULL, NULL);

   png_ptr->do_free |= PNG_FREE_STRUCT;

   return (png_ptr);
}


/* initialize png structure for reading, and allocate any memory needed */
/* This interface is depreciated in favour of the png_create_read_struct() */
void
png_read_init(png_structp png_ptr)
{
   jmp_buf tmp_jmp;  /* to save current jump buffer */

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

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

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

   /* initialize zbuf - compression buffer */
   png_ptr->zbuf_size = PNG_ZBUF_SIZE;
   png_ptr->zbuf = png_large_malloc(png_ptr, png_ptr->zbuf_size);

   png_ptr->zstream = (z_stream *)png_malloc(png_ptr, sizeof (z_stream));
   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, NULL, NULL);
}

/* read the information before the actual image data. */
void
png_read_info(png_structp png_ptr, png_infop info)
{
   png_byte chunk_start[8];
   png_uint_32 length;

   png_read_data(png_ptr, chunk_start, 8);
   if (!png_check_sig(chunk_start, 8))
   {
      if (!png_check_sig(chunk_start, 4))
         png_error(png_ptr, "Not a PNG file");
      else
         png_error(png_ptr, "PNG file corrupted by ASCII conversion");
   }

   while (1)
   {
      png_uint_32 crc;

      png_read_data(png_ptr, chunk_start, 8);
      length = png_get_uint_32(chunk_start);
      png_reset_crc(png_ptr);
      png_calculate_crc(png_ptr, chunk_start + 4, 4);
      if (!png_memcmp(chunk_start + 4, png_IHDR, 4))
         png_handle_IHDR(png_ptr, info, length);
      else if (!png_memcmp(chunk_start + 4, png_PLTE, 4))
         png_handle_PLTE(png_ptr, info, length);
      else if (!png_memcmp(chunk_start + 4, 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");

         png_ptr->idat_size = length;
         png_ptr->mode |= PNG_HAVE_IDAT;
         break;
      }
      else if (!png_memcmp(chunk_start + 4, png_IEND, 4))
         png_error(png_ptr, "No image in file");
#if defined(PNG_READ_gAMA_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_gAMA, 4))
         png_handle_gAMA(png_ptr, info, length);
#endif
#if defined(PNG_READ_sBIT_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_sBIT, 4))
         png_handle_sBIT(png_ptr, info, length);
#endif
#if defined(PNG_READ_cHRM_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_cHRM, 4))
         png_handle_cHRM(png_ptr, info, length);
#endif
#if defined(PNG_READ_tRNS_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_tRNS, 4))
         png_handle_tRNS(png_ptr, info, length);
#endif
#if defined(PNG_READ_bKGD_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_bKGD, 4))
         png_handle_bKGD(png_ptr, info, length);
#endif
#if defined(PNG_READ_hIST_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_hIST, 4))
         png_handle_hIST(png_ptr, info, length);
#endif
#if defined(PNG_READ_pHYs_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_pHYs, 4))
         png_handle_pHYs(png_ptr, info, length);
#endif
#if defined(PNG_READ_oFFs_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_oFFs, 4))
         png_handle_oFFs(png_ptr, info, length);
#endif
#if defined(PNG_READ_tIME_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_tIME, 4))
         png_handle_tIME(png_ptr, info, length);
#endif
#if defined(PNG_READ_tEXt_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_tEXt, 4))
         png_handle_tEXt(png_ptr, info, length);
#endif
#if defined(PNG_READ_zTXt_SUPPORTED)
      else if (!png_memcmp(chunk_start + 4, png_zTXt, 4))
         png_handle_zTXt(png_ptr, info, length);
#endif
      else
      {
         if (chunk_start[4] < 41 || chunk_start[4] > 122  ||
             (chunk_start[4] > 90 && chunk_start[4] < 97) ||
             chunk_start[5] < 41 || chunk_start[5] > 122  ||
             (chunk_start[5] > 90 && chunk_start[5] < 97) ||
             chunk_start[6] < 41 || chunk_start[6] > 122  ||
             (chunk_start[6] > 90 && chunk_start[6] < 97) ||
             chunk_start[7] < 41 || chunk_start[7] > 122  ||
             (chunk_start[7] > 90 && chunk_start[7] < 97))
         {
            char msg[45];

            sprintf(msg, "Invalid chunk type 0x%02X 0x%02X 0x%02X 0x%02X",
               chunk_start[4], chunk_start[5], chunk_start[6], chunk_start[7]);
            png_error(png_ptr, msg);
         }

         if ((chunk_start[4] & 0x20) == 0)
         {
            char msg[40];

            sprintf(msg, "Unknown critical chunk %c%c%c%c",
               chunk_start[4], chunk_start[5], chunk_start[6], chunk_start[7]);
            png_error(png_ptr, msg);
         }

         png_crc_skip(png_ptr, length);
      }
      png_read_data(png_ptr, chunk_start, 4);
      crc = png_get_uint_32(chunk_start);
      if (((crc ^ 0xffffffffL) & 0xffffffffL) != (png_ptr->crc & 0xffffffffL))
         png_error(png_ptr, "Bad CRC value");
   }
}

/* optional call to update the users info structure */
void
png_read_update_info(png_structp png_ptr, png_infop info)
{
   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
      png_read_start_row(png_ptr);
   png_read_transform_info(png_ptr, info);
}

/* initialize palette, background, etc, after transformations
   are set, but before any reading takes place.  This allows
   the user to obtail a gamma corrected palette, for example.
   If the user doesn't call this, we will do it ourselves. */
void
png_start_read_image(png_structp png_ptr)
{
   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
      png_read_start_row(png_ptr);
}

void
png_read_row(png_structp png_ptr, png_bytep row, png_bytep dsp_row)
{
   int ret;
   if (!(png_ptr->flags & PNG_FLAG_ROW_INIT))
      png_read_start_row(png_ptr);

#if defined(PNG_READ_INTERLACING_SUPPORTED)
   /* if interlaced and we do not need a new row, combine row and return */
   if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
   {
      switch (png_ptr->pass)
      {
         case 0:
            if (png_ptr->row_number & 7)
            {
               if (dsp_row)
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 1:
            if ((png_ptr->row_number & 7) || png_ptr->width < 5)
            {
               if (dsp_row)
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 2:
            if ((png_ptr->row_number & 7) != 4)
            {
               if (dsp_row && (png_ptr->row_number & 4))
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 3:
            if ((png_ptr->row_number & 3) || png_ptr->width < 3)
            {
               if (dsp_row)
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 4:
            if ((png_ptr->row_number & 3) != 2)
            {
               if (dsp_row && (png_ptr->row_number & 2))
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 5:
            if ((png_ptr->row_number & 1) || png_ptr->width < 2)
            {
               if (dsp_row)
                  png_combine_row(png_ptr, dsp_row,
                     png_pass_dsp_mask[png_ptr->pass]);
               png_read_finish_row(png_ptr);
               return;
            }
            break;
         case 6:
            if (!(png_ptr->row_number & 1))
            {
               png_read_finish_row(png_ptr);
               return;
            }
            break;
      }
   }
#endif

   if (!(png_ptr->mode & PNG_HAVE_IDAT))
      png_error(png_ptr, "Invalid attempt to read row data");

   png_ptr->zstream->next_out = png_ptr->row_buf;
   png_ptr->zstream->avail_out = (uInt)png_ptr->irowbytes;
   do
   {
      if (!(png_ptr->zstream->avail_in))
      {
         while (!png_ptr->idat_size)
         {
            png_byte buf[4];
            png_uint_32 crc;

            png_read_data(png_ptr, buf, 4);
            crc = png_get_uint_32(buf);
            if (((crc ^ 0xffffffffL) & 0xffffffffL) !=
               (png_ptr->crc & 0xffffffffL))
               png_error(png_ptr, "Bad CRC value");

            png_read_data(png_ptr, buf, 4);
            png_ptr->idat_size = png_get_uint_32(buf);
            png_reset_crc(png_ptr);

            png_crc_read(png_ptr, buf, 4);
            if (png_memcmp(buf, png_IDAT, 4))
               png_error(png_ptr, "Not enough IDATs for image");
         }
         png_ptr->zstream->avail_in = (uInt)png_ptr->zbuf_size;
         png_ptr->zstream->next_in = png_ptr->zbuf;
         if (png_ptr->zbuf_size > png_ptr->idat_size)
            png_ptr->zstream->avail_in = (uInt)png_ptr->idat_size;
         png_crc_read(png_ptr, png_ptr->zbuf, png_ptr->zstream->avail_in);
         png_ptr->idat_size -= png_ptr->zstream->avail_in;
      }
      ret = inflate(png_ptr->zstream, Z_PARTIAL_FLUSH);
      if (ret == Z_STREAM_END)
      {
         if (png_ptr->zstream->avail_out || png_ptr->zstream->avail_in ||
            png_ptr->idat_size)
            png_error(png_ptr, "Extra compressed data");
         png_ptr->mode |= PNG_AT_LAST_IDAT;
         png_ptr->flags |= PNG_FLAG_ZLIB_FINISHED;
         break;
      }
      if (ret != Z_OK)
         png_error(png_ptr, png_ptr->zstream->msg ? png_ptr->zstream->msg :
                   "Decompression error");
   } while (png_ptr->zstream->avail_out);

   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_ptr->row_info.width *
      (png_uint_32)png_ptr->row_info.pixel_depth + 7) >> 3);

   png_read_filter_row(png_ptr, &(png_ptr->row_info),