pngwrite.c

一个国人自己实现图像库的程序（有参考价值）

/* pngwrite.c - general routines to write 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.)
 */

/* get internal access to png.h */
#define PNG_INTERNAL
#include "png.h"
#ifdef PNG_WRITE_SUPPORTED

/* Writes all the PNG information.  This is the suggested way to use the
 * library.  If you have a new chunk to add, make a function to write it,
 * and put it in the correct location here.  If you want the chunk written
 * after the image data, put it in png_write_end().  I strongly encourage
 * you to supply a PNG_INFO_ flag, and check info_ptr->valid before writing
 * the chunk, as that will keep the code from breaking if you want to just
 * write a plain PNG file.  If you have long comments, I suggest writing
 * them in png_write_end(), and compressing them.
 */
void PNGAPI
png_write_info_before_PLTE(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_write_info_before_PLTE\n");
   if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
   {
   png_write_sig(png_ptr); /* write PNG signature */
#if defined(PNG_MNG_FEATURES_SUPPORTED)
   if((png_ptr->mode&PNG_HAVE_PNG_SIGNATURE)&&(png_ptr->mng_features_permitted))
   {
      png_warning(png_ptr,"MNG features are not allowed in a PNG datastream\n");
      png_ptr->mng_features_permitted=0;
   }
#endif
   /* write IHDR information. */
   png_write_IHDR(png_ptr, info_ptr->width, info_ptr->height,
      info_ptr->bit_depth, info_ptr->color_type, info_ptr->compression_type,
      info_ptr->filter_type,
#if defined(PNG_WRITE_INTERLACING_SUPPORTED)
      info_ptr->interlace_type);
#else
      0);
#endif
   /* the rest of these check to see if the valid field has the appropriate
      flag set, and if it does, writes the chunk. */
#if defined(PNG_WRITE_gAMA_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_gAMA)
   {
#  ifdef PNG_FLOATING_POINT_SUPPORTED
      png_write_gAMA(png_ptr, info_ptr->gamma);
#else
#ifdef PNG_FIXED_POINT_SUPPORTED
      png_write_gAMA_fixed(png_ptr, info_ptr->int_gamma);
#  endif
#endif
   }
#endif
#if defined(PNG_WRITE_sRGB_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_sRGB)
      png_write_sRGB(png_ptr, (int)info_ptr->srgb_intent);
#endif
#if defined(PNG_WRITE_iCCP_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_iCCP)
      png_write_iCCP(png_ptr, info_ptr->iccp_name, PNG_COMPRESSION_TYPE_BASE,
                     info_ptr->iccp_profile, (int)info_ptr->iccp_proflen);
#endif
#if defined(PNG_WRITE_sBIT_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_sBIT)
      png_write_sBIT(png_ptr, &(info_ptr->sig_bit), info_ptr->color_type);
#endif
#if defined(PNG_WRITE_cHRM_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_cHRM)
   {
#ifdef PNG_FLOATING_POINT_SUPPORTED
      png_write_cHRM(png_ptr,
         info_ptr->x_white, info_ptr->y_white,
         info_ptr->x_red, info_ptr->y_red,
         info_ptr->x_green, info_ptr->y_green,
         info_ptr->x_blue, info_ptr->y_blue);
#else
#  ifdef PNG_FIXED_POINT_SUPPORTED
      png_write_cHRM_fixed(png_ptr,
         info_ptr->int_x_white, info_ptr->int_y_white,
         info_ptr->int_x_red, info_ptr->int_y_red,
         info_ptr->int_x_green, info_ptr->int_y_green,
         info_ptr->int_x_blue, info_ptr->int_y_blue);
#  endif
#endif
   }
#endif
#if defined(PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED)
   if (info_ptr->unknown_chunks_num)
   {
       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_HAVE_PLTE)) &&
            ((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_WROTE_INFO_BEFORE_PLTE;
   }
}

void PNGAPI
png_write_info(png_structp png_ptr, png_infop info_ptr)
{
#if defined(PNG_WRITE_TEXT_SUPPORTED) || defined(PNG_WRITE_sPLT_SUPPORTED)
   int i;
#endif

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

   png_write_info_before_PLTE(png_ptr, info_ptr);

   if (info_ptr->valid & PNG_INFO_PLTE)
      png_write_PLTE(png_ptr, info_ptr->palette,
         (png_uint_32)info_ptr->num_palette);
   else if (info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
      png_error(png_ptr, "Valid palette required for paletted images\n");

#if defined(PNG_WRITE_tRNS_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_tRNS)
      {
#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
         /* invert the alpha channel (in tRNS) */
         if ((png_ptr->transformations & PNG_INVERT_ALPHA) &&
            info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)
         {
            int j;
            for (j=0; j<(int)info_ptr->num_trans; j++)
               info_ptr->trans[j] = (png_byte)(255 - info_ptr->trans[j]);
         }
#endif
      png_write_tRNS(png_ptr, info_ptr->trans, &(info_ptr->trans_values),
         info_ptr->num_trans, info_ptr->color_type);
      }
#endif
#if defined(PNG_WRITE_bKGD_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_bKGD)
      png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
#endif
#if defined(PNG_WRITE_hIST_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_hIST)
      png_write_hIST(png_ptr, info_ptr->hist, info_ptr->num_palette);
#endif
#if defined(PNG_WRITE_oFFs_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_oFFs)
      png_write_oFFs(png_ptr, info_ptr->x_offset, info_ptr->y_offset,
         info_ptr->offset_unit_type);
#endif
#if defined(PNG_WRITE_pCAL_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_pCAL)
      png_write_pCAL(png_ptr, info_ptr->pcal_purpose, info_ptr->pcal_X0,
         info_ptr->pcal_X1, info_ptr->pcal_type, info_ptr->pcal_nparams,
         info_ptr->pcal_units, info_ptr->pcal_params);
#endif
#if defined(PNG_WRITE_sCAL_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_sCAL)
#if defined(PNG_FLOATING_POINT_SUPPORTED) && !defined(PNG_NO_STDIO)
      png_write_sCAL(png_ptr, (int)info_ptr->scal_unit,
          info_ptr->scal_pixel_width, info_ptr->scal_pixel_height);
#else
#ifdef PNG_FIXED_POINT_SUPPORTED
      png_write_sCAL_s(png_ptr, (int)info_ptr->scal_unit,
          info_ptr->scal_s_width, info_ptr->scal_s_height);
#else
      png_warning(png_ptr,
          "png_write_sCAL not supported; sCAL chunk not written.\n");
#endif
#endif
#endif
#if defined(PNG_WRITE_pHYs_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_pHYs)
      png_write_pHYs(png_ptr, info_ptr->x_pixels_per_unit,
         info_ptr->y_pixels_per_unit, info_ptr->phys_unit_type);
#endif
#if defined(PNG_WRITE_tIME_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_tIME)
   {
      png_write_tIME(png_ptr, &(info_ptr->mod_time));
      png_ptr->mode |= PNG_WROTE_tIME;
   }
#endif
#if defined(PNG_WRITE_sPLT_SUPPORTED)
   if (info_ptr->valid & PNG_INFO_sPLT)
     for (i = 0; i < (int)info_ptr->splt_palettes_num; i++)
       png_write_sPLT(png_ptr, info_ptr->splt_palettes + i);
#endif
#if defined(PNG_WRITE_TEXT_SUPPORTED)
   /* Check to see if we need to write text chunks */
   for (i = 0; i < info_ptr->num_text; i++)
   {
      png_debug2(2, "Writing header text chunk %d, type %d\n", i,
         info_ptr->text[i].compression);
      /* an internationalized chunk? */
      if (info_ptr->text[i].compression > 0)
      {
#if defined(PNG_WRITE_iTXt_SUPPORTED)
          /* write international chunk */
          png_write_iTXt(png_ptr,
                         info_ptr->text[i].compression,
                         info_ptr->text[i].key,
                         info_ptr->text[i].lang,
                         info_ptr->text[i].lang_key,
                         info_ptr->text[i].text);
#else
          png_warning(png_ptr, "Unable to write international text\n");
#endif
          /* Mark this chunk as written */
          info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
      }
      /* If we want a compressed text chunk */
      else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_zTXt)
      {
#if defined(PNG_WRITE_zTXt_SUPPORTED)
         /* write compressed chunk */
         png_write_zTXt(png_ptr, info_ptr->text[i].key,
            info_ptr->text[i].text, 0,
            info_ptr->text[i].compression);
#else
         png_warning(png_ptr, "Unable to write compressed text\n");
#endif
         /* Mark this chunk as written */
         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
      }
      else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
      {
#if defined(PNG_WRITE_tEXt_SUPPORTED)
         /* write uncompressed chunk */
         png_write_tEXt(png_ptr, info_ptr->text[i].key,
                         info_ptr->text[i].text,
                         0);
#else
         png_warning(png_ptr, "Unable to write uncompressed text\n");
#endif
         /* Mark this chunk as written */
         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
      }
   }
#endif
#if defined(PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED)
   if (info_ptr->unknown_chunks_num)
   {
       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_HAVE_PLTE) &&
            !(up->location & PNG_HAVE_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
}

/* Writes the end of the PNG file.  If you don't want to write comments or
 * time information, you can pass NULL for info.  If you already wrote these
 * in png_write_info(), do not write them again here.  If you have long
 * comments, I suggest writing them here, and compressing them.
 */
void PNGAPI
png_write_end(png_structp png_ptr, png_infop info_ptr)
{
   png_debug(1, "in png_write_end\n");
   if (!(png_ptr->mode & PNG_HAVE_IDAT))
      png_error(png_ptr, "No IDATs written into file");

   /* see if user wants us to write information chunks */
   if (info_ptr != NULL)
   {
#if defined(PNG_WRITE_TEXT_SUPPORTED)
      int i; /* local index variable */
#endif
#if defined(PNG_WRITE_tIME_SUPPORTED)
      /* check to see if user has supplied a time chunk */
      if ((info_ptr->valid & PNG_INFO_tIME) &&
         !(png_ptr->mode & PNG_WROTE_tIME))
         png_write_tIME(png_ptr, &(info_ptr->mod_time));
#endif
#if defined(PNG_WRITE_TEXT_SUPPORTED)
      /* loop through comment chunks */
      for (i = 0; i < info_ptr->num_text; i++)
      {
         png_debug2(2, "Writing trailer text chunk %d, type %d\n", i,
            info_ptr->text[i].compression);
         /* an internationalized chunk? */
         if (info_ptr->text[i].compression > 0)
         {
#if defined(PNG_WRITE_iTXt_SUPPORTED)
             /* write international chunk */
             png_write_iTXt(png_ptr,
                         info_ptr->text[i].compression,
                         info_ptr->text[i].key,
                         info_ptr->text[i].lang,
                         info_ptr->text[i].lang_key,
                         info_ptr->text[i].text);
#else
             png_warning(png_ptr, "Unable to write international text\n");
#endif
             /* Mark this chunk as written */
             info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
         }
         else if (info_ptr->text[i].compression >= PNG_TEXT_COMPRESSION_zTXt)
         {
#if defined(PNG_WRITE_zTXt_SUPPORTED)
            /* write compressed chunk */
            png_write_zTXt(png_ptr, info_ptr->text[i].key,
               info_ptr->text[i].text, 0,
               info_ptr->text[i].compression);
#else
            png_warning(png_ptr, "Unable to write compressed text\n");
#endif
            /* Mark this chunk as written */
            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;
         }
         else if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)
         {
#if defined(PNG_WRITE_tEXt_SUPPORTED)
            /* write uncompressed chunk */
            png_write_tEXt(png_ptr, info_ptr->text[i].key,
               info_ptr->text[i].text, 0);
#else
            png_warning(png_ptr, "Unable to write uncompressed text\n");
#endif

            /* Mark this chunk as written */
            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
         }
      }
#endif
#if defined(PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED)
   if (info_ptr->unknown_chunks_num)