pngwrite.c

一个国人自己实现图像库的程序（有参考价值）

   {
       png_unknown_chunk *up;

       png_debug(5, "writing extra chunks\n");

       for (up = info_ptr->unknown_chunks;
            up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;
            up++)
       {
         int keep=png_handle_as_unknown(png_ptr, up->name);
         if (keep != HANDLE_CHUNK_NEVER &&
            up->location && (up->location & PNG_AFTER_IDAT) &&
            ((up->name[3] & 0x20) || keep == HANDLE_CHUNK_ALWAYS ||
            (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS)))
         {
            png_write_chunk(png_ptr, up->name, up->data, up->size);
         }
       }
   }
#endif
   }

   png_ptr->mode |= PNG_AFTER_IDAT;

   /* write end of PNG file */
   png_write_IEND(png_ptr);
#if 0
/* This flush, added in libpng-1.0.8,  causes some applications to crash
   because they do not set png_ptr->output_flush_fn */
   png_flush(png_ptr);
#endif
}

#if defined(PNG_WRITE_tIME_SUPPORTED)
#if !defined(_WIN32_WCE)
/* "time.h" functions are not supported on WindowsCE */
void PNGAPI
png_convert_from_struct_tm(png_timep ptime, struct tm FAR * ttime)
{
   png_debug(1, "in png_convert_from_struct_tm\n");
   ptime->year = (png_uint_16)(1900 + ttime->tm_year);
   ptime->month = (png_byte)(ttime->tm_mon + 1);
   ptime->day = (png_byte)ttime->tm_mday;
   ptime->hour = (png_byte)ttime->tm_hour;
   ptime->minute = (png_byte)ttime->tm_min;
   ptime->second = (png_byte)ttime->tm_sec;
}

void PNGAPI
png_convert_from_time_t(png_timep ptime, time_t ttime)
{
   struct tm *tbuf;

   png_debug(1, "in png_convert_from_time_t\n");
   tbuf = gmtime(&ttime);
   png_convert_from_struct_tm(ptime, tbuf);
}
#endif
#endif

/* Initialize png_ptr structure, and allocate any memory needed */
png_structp PNGAPI
png_create_write_struct(png_const_charp user_png_ver, png_voidp error_ptr,
   png_error_ptr error_fn, png_error_ptr warn_fn)
{
#ifdef PNG_USER_MEM_SUPPORTED
   return (png_create_write_struct_2(user_png_ver, error_ptr, error_fn,
      warn_fn, png_voidp_NULL, png_malloc_ptr_NULL, png_free_ptr_NULL));
}

/* Alternate initialize png_ptr structure, and allocate any memory needed */
png_structp PNGAPI
png_create_write_struct_2(png_const_charp user_png_ver, png_voidp error_ptr,
   png_error_ptr error_fn, png_error_ptr warn_fn, png_voidp mem_ptr,
   png_malloc_ptr malloc_fn, png_free_ptr free_fn)
{
#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_write_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 /* PNG_USER_MEM_SUPPORTED */
      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_USER_MEM_SUPPORTED */
   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_set_write_fn(png_ptr, png_voidp_NULL, png_rw_ptr_NULL,
      png_flush_ptr_NULL);

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
   png_set_filter_heuristics(png_ptr, PNG_FILTER_HEURISTIC_DEFAULT,
      1, png_doublep_NULL, png_doublep_NULL);
#endif

   return ((png_structp)png_ptr);
}

/* Initialize png_ptr structure, and allocate any memory needed */
#undef png_write_init
void PNGAPI
png_write_init(png_structp png_ptr)
{
   /* We only come here via pre-1.0.7-compiled applications */
   png_write_init_2(png_ptr, "1.0.6 or earlier", 0, 0);
}

#undef png_write_init_2
void PNGAPI
png_write_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 writing 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 the application for writing is too small.");
     }
   png_write_init_3(&png_ptr, user_png_ver, png_struct_size);
}


void PNGAPI
png_write_init_3(png_structpp ptr_ptr, png_const_charp user_png_ver,
   png_size_t png_struct_size)
{
   png_structp png_ptr=*ptr_ptr;
#ifdef PNG_SETJMP_SUPPORTED
   jmp_buf tmp_jmp; /* to save current jump buffer */
#endif
   int i = 0;
   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_write_init() and should be recompiled.");
       break;
#endif
     }
   } while (png_libpng_ver[i++]);

   png_debug(1, "in png_write_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);
       png_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG);
       *ptr_ptr = png_ptr;
     }

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

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

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

   png_set_write_fn(png_ptr, png_voidp_NULL, png_rw_ptr_NULL,
      png_flush_ptr_NULL);

   /* 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);

#if defined(PNG_WRITE_WEIGHTED_FILTER_SUPPORTED)
   png_set_filter_heuristics(png_ptr, PNG_FILTER_HEURISTIC_DEFAULT,
      1, png_doublep_NULL, png_doublep_NULL);
#endif
}

/* Write a few rows of image data.  If the image is interlaced,
 * either you will have to write the 7 sub images, or, if you
 * have called png_set_interlace_handling(), you will have to
 * "write" the image seven times.
 */
void PNGAPI
png_write_rows(png_structp png_ptr, png_bytepp row,
   png_uint_32 num_rows)
{
   png_uint_32 i; /* row counter */
   png_bytepp rp; /* row pointer */

   png_debug(1, "in png_write_rows\n");
   /* loop through the rows */
   for (i = 0, rp = row; i < num_rows; i++, rp++)
   {
      png_write_row(png_ptr, *rp);
   }
}

/* Write the image.  You only need to call this function once, even
 * if you are writing an interlaced image.
 */
void PNGAPI
png_write_image(png_structp png_ptr, png_bytepp image)
{
   png_uint_32 i; /* row index */
   int pass, num_pass; /* pass variables */
   png_bytepp rp; /* points to current row */

   png_debug(1, "in png_write_image\n");
#if defined(PNG_WRITE_INTERLACING_SUPPORTED)
   /* intialize interlace handling.  If image is not interlaced,
      this will set pass to 1 */
   num_pass = png_set_interlace_handling(png_ptr);
#else
   num_pass = 1;
#endif
   /* loop through passes */
   for (pass = 0; pass < num_pass; pass++)
   {
      /* loop through image */
      for (i = 0, rp = image; i < png_ptr->height; i++, rp++)
      {
         png_write_row(png_ptr, *rp);
      }
   }
}

/* called by user to write a row of image data */
void PNGAPI
png_write_row(png_structp png_ptr, png_bytep row)
{
   png_debug2(1, "in png_write_row (row %ld, pass %d)\n",
      png_ptr->row_number, png_ptr->pass);
   /* initialize transformations and other stuff if first time */
   if (png_ptr->row_number == 0 && png_ptr->pass == 0)
   {
   /* make sure we wrote the header info */
   if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
      png_error(png_ptr,
         "png_write_info was never called before png_write_row.");

   /* check for transforms that have been set but were defined out */
#if !defined(PNG_WRITE_INVERT_SUPPORTED) && defined(PNG_READ_INVERT_SUPPORTED)
   if (png_ptr->transformations & PNG_INVERT_MONO)
      png_warning(png_ptr, "PNG_WRITE_INVERT_SUPPORTED is not defined.");
#endif
#if !defined(PNG_WRITE_FILLER_SUPPORTED) && defined(PNG_READ_FILLER_SUPPORTED)