text: 
  /* pngwrite.c - general routines to write a PNG file
   *
   * Last changed in libpng 1.5.4 [July 7, 2011]
   * Copyright (c) 1998-2011 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 code is released under the libpng license.
   * For conditions of distribution and use, see the disclaimer
   * and license in png.h
   */
  
  #include "pngpriv.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");
  
     if (png_ptr == NULL || info_ptr == NULL)
        return;
  
     if (!(png_ptr->mode & PNG_WROTE_INFO_BEFORE_PLTE))
     {
     /* Write PNG signature */
     png_write_sig(png_ptr);
  
  #ifdef 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");
        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,
  #ifdef 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.
      */
  #ifdef PNG_WRITE_gAMA_SUPPORTED
     if (info_ptr->valid & PNG_INFO_gAMA)
        png_write_gAMA_fixed(png_ptr, info_ptr->gamma);
  #endif
  #ifdef PNG_WRITE_sRGB_SUPPORTED
     if (info_ptr->valid & PNG_INFO_sRGB)
        png_write_sRGB(png_ptr, (int)info_ptr->srgb_intent);
  #endif
  
  #ifdef PNG_WRITE_iCCP_SUPPORTED
     if (info_ptr->valid & PNG_INFO_iCCP)
        png_write_iCCP(png_ptr, info_ptr->iccp_name, PNG_COMPRESSION_TYPE_BASE,
            (png_charp)info_ptr->iccp_profile, (int)info_ptr->iccp_proflen);
  #endif
  #ifdef 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
  #ifdef PNG_WRITE_cHRM_SUPPORTED
     if (info_ptr->valid & PNG_INFO_cHRM)
        png_write_cHRM_fixed(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);
  #endif
  
  #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
     if (info_ptr->unknown_chunks_num)
     {
        png_unknown_chunk *up;
  
        png_debug(5, "writing extra chunks");
  
        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 != PNG_HANDLE_CHUNK_NEVER &&
               up->location &&
               !(up->location & PNG_HAVE_PLTE) &&
               !(up->location & PNG_HAVE_IDAT) &&
               !(up->location & PNG_AFTER_IDAT) &&
               ((up->name[3] & 0x20) || keep == PNG_HANDLE_CHUNK_ALWAYS ||
               (png_ptr->flags & PNG_FLAG_KEEP_UNSAFE_CHUNKS)))
           {
              if (up->size == 0)
                 png_warning(png_ptr, "Writing zero-length unknown chunk");
  
              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");
  
     if (png_ptr == NULL || info_ptr == NULL)
        return;
  
     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");
  
  #ifdef PNG_WRITE_tRNS_SUPPORTED
     if (info_ptr->valid & PNG_INFO_tRNS)
     {
  #ifdef 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_alpha[j] =
                 (png_byte)(255 - info_ptr->trans_alpha[j]);
        }
  #endif
        png_write_tRNS(png_ptr, info_ptr->trans_alpha, &(info_ptr->trans_color),
            info_ptr->num_trans, info_ptr->color_type);
     }
  #endif
  #ifdef PNG_WRITE_bKGD_SUPPORTED
     if (info_ptr->valid & PNG_INFO_bKGD)
        png_write_bKGD(png_ptr, &(info_ptr->background), info_ptr->color_type);
  #endif
  
  #ifdef PNG_WRITE_hIST_SUPPORTED
     if (info_ptr->valid & PNG_INFO_hIST)
        png_write_hIST(png_ptr, info_ptr->hist, info_ptr->num_palette);
  #endif
  
  #ifdef 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
  
  #ifdef 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
  
  #ifdef PNG_WRITE_sCAL_SUPPORTED
     if (info_ptr->valid & PNG_INFO_sCAL)
        png_write_sCAL_s(png_ptr, (int)info_ptr->scal_unit,
            info_ptr->scal_s_width, info_ptr->scal_s_height);
  #endif /* sCAL */
  
  #ifdef 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 /* pHYs */
  
  #ifdef 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 /* tIME */
  
  #ifdef 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 /* sPLT */
  
  #ifdef 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", i,
            info_ptr->text[i].compression);
        /* An internationalized chunk? */
        if (info_ptr->text[i].compression > 0)
        {
  #ifdef 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");
  #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)
        {
  #ifdef 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");
  #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)
        {
  #ifdef PNG_WRITE_tEXt_SUPPORTED
           /* Write uncompressed chunk */
           png_write_tEXt(png_ptr, info_ptr->text[i].key,
               info_ptr->text[i].text,
               0);
           /* Mark this chunk as written */
           info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
  #else
           /* Can't get here */
           png_warning(png_ptr, "Unable to write uncompressed text");
  #endif
        }
     }
  #endif /* tEXt */
  
  #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
     if (info_ptr->unknown_chunks_num)
     {
        png_unknown_chunk *up;
  
        png_debug(5, "writing extra chunks");
  
        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 != PNG_HANDLE_CHUNK_NEVER &&
               up->location &&
               (up->location & PNG_HAVE_PLTE) &&
               !(up->location & PNG_HAVE_IDAT) &&
               !(up->location & PNG_AFTER_IDAT) &&
               ((up->name[3] & 0x20) || keep == PNG_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");
  
     if (png_ptr == NULL)
        return;
  
     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)
     {
  #ifdef PNG_WRITE_TEXT_SUPPORTED
        int i; /* local index variable */
  #endif
  #ifdef 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
  #ifdef 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", i,
              info_ptr->text[i].compression);
           /* An internationalized chunk? */
           if (info_ptr->text[i].compression > 0)
           {
  #ifdef 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");
  #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)
           {
  #ifdef 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");
  #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)
           {
  #ifdef 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");
  #endif
  
              /* Mark this chunk as written */
              info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;
           }
        }
  #endif
  #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED
     if (info_ptr->unknown_chunks_num)
     {
        png_unknown_chunk *up;
  
        png_debug(5, "writing extra chunks");
  
        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 != PNG_HANDLE_CHUNK_NEVER &&
               up->location &&
               (up->location & PNG_AFTER_IDAT) &&
               ((up->name[3] & 0x20) || keep == PNG_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);
     /* This flush, added in libpng-1.0.8, removed from libpng-1.0.9beta03,
      * and restored again in libpng-1.2.30, may cause some applications that
      * do not set png_ptr->output_flush_fn to crash.  If your application
      * experiences a problem, please try building libpng with
      * PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED defined, and report the event to
      * png-mng-implement at lists.sf.net .
      */
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  #  ifdef PNG_WRITE_FLUSH_AFTER_IEND_SUPPORTED
     png_flush(png_ptr);
  #  endif
  #endif
  }
  
  #ifdef PNG_CONVERT_tIME_SUPPORTED
  /* "tm" structure is not supported on WindowsCE */
  void PNGAPI
  png_convert_from_struct_tm(png_timep ptime, PNG_CONST struct tm FAR * ttime)
  {
     png_debug(1, "in png_convert_from_struct_tm");
  
     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");
  
     tbuf = gmtime(&ttime);
     png_convert_from_struct_tm(ptime, tbuf);
  }
  #endif
  
  /* Initialize png_ptr structure, and allocate any memory needed */
  PNG_FUNCTION(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),PNG_ALLOCATED)
  {
  #ifdef PNG_USER_MEM_SUPPORTED
     return (png_create_write_struct_2(user_png_ver, error_ptr, error_fn,
         warn_fn, NULL, NULL, NULL));
  }
  
  /* Alternate initialize png_ptr structure, and allocate any memory needed */
  static void png_reset_filter_heuristics(png_structp png_ptr); /* forward decl */
  
  PNG_FUNCTION(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),PNG_ALLOCATED)
  {
  #endif /* PNG_USER_MEM_SUPPORTED */
     volatile int png_cleanup_needed = 0;
  #ifdef PNG_SETJMP_SUPPORTED
     volatile
  #endif
     png_structp png_ptr;
  #ifdef PNG_SETJMP_SUPPORTED
  #ifdef USE_FAR_KEYWORD
     jmp_buf tmp_jmpbuf;
  #endif
  #endif
  
     png_debug(1, "in png_create_write_struct");
  
  #ifdef PNG_USER_MEM_SUPPORTED
     png_ptr = (png_structp)png_create_struct_2(PNG_STRUCT_PNG,
         (png_malloc_ptr)malloc_fn, (png_voidp)mem_ptr);
  #else
     png_ptr = (png_structp)png_create_struct(PNG_STRUCT_PNG);
  #endif /* PNG_USER_MEM_SUPPORTED */
     if (png_ptr == NULL)
        return (NULL);
  
     /* Added at libpng-1.2.6 */
  #ifdef PNG_SET_USER_LIMITS_SUPPORTED
     png_ptr->user_width_max = PNG_USER_WIDTH_MAX;
     png_ptr->user_height_max = PNG_USER_HEIGHT_MAX;
  #endif
  
  #ifdef PNG_SETJMP_SUPPORTED
  /* Applications that neglect to set up their own setjmp() and then
     encounter a png_error() will longjmp here.  Since the jmpbuf is
     then meaningless we abort instead of returning. */
  #ifdef USE_FAR_KEYWORD
     if (setjmp(tmp_jmpbuf))
  #else
     if (setjmp(png_jmpbuf(png_ptr))) /* sets longjmp to match setjmp */
  #endif
  #ifdef USE_FAR_KEYWORD
     png_memcpy(png_jmpbuf(png_ptr), tmp_jmpbuf, png_sizeof(jmp_buf));
  #endif
        PNG_ABORT();
  #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);
  
     if (!png_user_version_check(png_ptr, user_png_ver))
        png_cleanup_needed = 1;
  
     /* Initialize zbuf - compression buffer */
     png_ptr->zbuf_size = PNG_ZBUF_SIZE;
  
     if (!png_cleanup_needed)
     {
        png_ptr->zbuf = (png_bytep)png_malloc_warn(png_ptr,
            png_ptr->zbuf_size);
        if (png_ptr->zbuf == NULL)
           png_cleanup_needed = 1;
     }
  
     if (png_cleanup_needed)
     {
         /* Clean up PNG structure and deallocate any memory. */
         png_free(png_ptr, png_ptr->zbuf);
         png_ptr->zbuf = NULL;
  #ifdef PNG_USER_MEM_SUPPORTED
         png_destroy_struct_2((png_voidp)png_ptr,
             (png_free_ptr)free_fn, (png_voidp)mem_ptr);
  #else
         png_destroy_struct((png_voidp)png_ptr);
  #endif
         return (NULL);
     }
  
     png_set_write_fn(png_ptr, NULL, NULL, NULL);
  
  #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
     png_reset_filter_heuristics(png_ptr);
  #endif
  
     return (png_ptr);
  }
  
  
  /* 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");
  
     if (png_ptr == NULL)
        return;
  
     /* 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 */
  
     if (png_ptr == NULL)
        return;
  
     png_debug(1, "in png_write_image");
  
  #ifdef PNG_WRITE_INTERLACING_SUPPORTED
     /* Initialize 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_const_bytep row)
  {
     if (png_ptr == NULL)
        return;
  
     png_debug2(1, "in png_write_row (row %u, pass %d)",
        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)
        if (png_ptr->transformations & PNG_FILLER)
           png_warning(png_ptr, "PNG_WRITE_FILLER_SUPPORTED is not defined");
  #endif
  #if !defined(PNG_WRITE_PACKSWAP_SUPPORTED) && \
      defined(PNG_READ_PACKSWAP_SUPPORTED)
        if (png_ptr->transformations & PNG_PACKSWAP)
           png_warning(png_ptr,
               "PNG_WRITE_PACKSWAP_SUPPORTED is not defined");
  #endif
  
  #if !defined(PNG_WRITE_PACK_SUPPORTED) && defined(PNG_READ_PACK_SUPPORTED)
        if (png_ptr->transformations & PNG_PACK)
           png_warning(png_ptr, "PNG_WRITE_PACK_SUPPORTED is not defined");
  #endif
  
  #if !defined(PNG_WRITE_SHIFT_SUPPORTED) && defined(PNG_READ_SHIFT_SUPPORTED)
        if (png_ptr->transformations & PNG_SHIFT)
           png_warning(png_ptr, "PNG_WRITE_SHIFT_SUPPORTED is not defined");
  #endif
  
  #if !defined(PNG_WRITE_BGR_SUPPORTED) && defined(PNG_READ_BGR_SUPPORTED)
        if (png_ptr->transformations & PNG_BGR)
           png_warning(png_ptr, "PNG_WRITE_BGR_SUPPORTED is not defined");
  #endif
  
  #if !defined(PNG_WRITE_SWAP_SUPPORTED) && defined(PNG_READ_SWAP_SUPPORTED)
        if (png_ptr->transformations & PNG_SWAP_BYTES)
           png_warning(png_ptr, "PNG_WRITE_SWAP_SUPPORTED is not defined");
  #endif
  
        png_write_start_row(png_ptr);
     }
  
  #ifdef PNG_WRITE_INTERLACING_SUPPORTED
     /* If interlaced and not interested in row, return */
     if (png_ptr->interlaced && (png_ptr->transformations & PNG_INTERLACE))
     {
        switch (png_ptr->pass)
        {
           case 0:
              if (png_ptr->row_number & 0x07)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 1:
              if ((png_ptr->row_number & 0x07) || png_ptr->width < 5)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 2:
              if ((png_ptr->row_number & 0x07) != 4)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 3:
              if ((png_ptr->row_number & 0x03) || png_ptr->width < 3)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 4:
              if ((png_ptr->row_number & 0x03) != 2)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 5:
              if ((png_ptr->row_number & 0x01) || png_ptr->width < 2)
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           case 6:
              if (!(png_ptr->row_number & 0x01))
              {
                 png_write_finish_row(png_ptr);
                 return;
              }
              break;
  
           default: /* error: ignore it */
              break;
        }
     }
  #endif
  
     /* Set up row info for transformations */
     png_ptr->row_info.color_type = png_ptr->color_type;
     png_ptr->row_info.width = png_ptr->usr_width;
     png_ptr->row_info.channels = png_ptr->usr_channels;
     png_ptr->row_info.bit_depth = png_ptr->usr_bit_depth;
     png_ptr->row_info.pixel_depth = (png_byte)(png_ptr->row_info.bit_depth *
        png_ptr->row_info.channels);
  
     png_ptr->row_info.rowbytes = PNG_ROWBYTES(png_ptr->row_info.pixel_depth,
        png_ptr->row_info.width);
  
     png_debug1(3, "row_info->color_type = %d", png_ptr->row_info.color_type);
     png_debug1(3, "row_info->width = %u", png_ptr->row_info.width);
     png_debug1(3, "row_info->channels = %d", png_ptr->row_info.channels);
     png_debug1(3, "row_info->bit_depth = %d", png_ptr->row_info.bit_depth);
     png_debug1(3, "row_info->pixel_depth = %d", png_ptr->row_info.pixel_depth);
     png_debug1(3, "row_info->rowbytes = %lu",
         (unsigned long)png_ptr->row_info.rowbytes);
  
     /* Copy user's row into buffer, leaving room for filter byte. */
     png_memcpy(png_ptr->row_buf + 1, row, png_ptr->row_info.rowbytes);
  
  #ifdef PNG_WRITE_INTERLACING_SUPPORTED
     /* Handle interlacing */
     if (png_ptr->interlaced && png_ptr->pass < 6 &&
         (png_ptr->transformations & PNG_INTERLACE))
     {
        png_do_write_interlace(&(png_ptr->row_info),
            png_ptr->row_buf + 1, png_ptr->pass);
        /* This should always get caught above, but still ... */
        if (!(png_ptr->row_info.width))
        {
           png_write_finish_row(png_ptr);
           return;
        }
     }
  #endif
  
  #ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
     /* Handle other transformations */
     if (png_ptr->transformations)
        png_do_write_transformations(png_ptr);
  #endif
  
  #ifdef PNG_MNG_FEATURES_SUPPORTED
     /* Write filter_method 64 (intrapixel differencing) only if
      * 1. Libpng was compiled with PNG_MNG_FEATURES_SUPPORTED and
      * 2. Libpng did not write a PNG signature (this filter_method is only
      *    used in PNG datastreams that are embedded in MNG datastreams) and
      * 3. The application called png_permit_mng_features with a mask that
      *    included PNG_FLAG_MNG_FILTER_64 and
      * 4. The filter_method is 64 and
      * 5. The color_type is RGB or RGBA
      */
     if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
         (png_ptr->filter_type == PNG_INTRAPIXEL_DIFFERENCING))
     {
        /* Intrapixel differencing */
        png_do_write_intrapixel(&(png_ptr->row_info), png_ptr->row_buf + 1);
     }
  #endif
  
     /* Find a filter if necessary, filter the row and write it out. */
     png_write_find_filter(png_ptr, &(png_ptr->row_info));
  
     if (png_ptr->write_row_fn != NULL)
        (*(png_ptr->write_row_fn))(png_ptr, png_ptr->row_number, png_ptr->pass);
  }
  
  #ifdef PNG_WRITE_FLUSH_SUPPORTED
  /* Set the automatic flush interval or 0 to turn flushing off */
  void PNGAPI
  png_set_flush(png_structp png_ptr, int nrows)
  {
     png_debug(1, "in png_set_flush");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flush_dist = (nrows < 0 ? 0 : nrows);
  }
  
  /* Flush the current output buffers now */
  void PNGAPI
  png_write_flush(png_structp png_ptr)
  {
     int wrote_IDAT;
  
     png_debug(1, "in png_write_flush");
  
     if (png_ptr == NULL)
        return;
  
     /* We have already written out all of the data */
     if (png_ptr->row_number >= png_ptr->num_rows)
        return;
  
     do
     {
        int ret;
  
        /* Compress the data */
        ret = deflate(&png_ptr->zstream, Z_SYNC_FLUSH);
        wrote_IDAT = 0;
  
        /* Check for compression errors */
        if (ret != Z_OK)
        {
           if (png_ptr->zstream.msg != NULL)
              png_error(png_ptr, png_ptr->zstream.msg);
  
           else
              png_error(png_ptr, "zlib error");
        }
  
        if (!(png_ptr->zstream.avail_out))
        {
           /* Write the IDAT and reset the zlib output buffer */
           png_write_IDAT(png_ptr, png_ptr->zbuf, png_ptr->zbuf_size);
           wrote_IDAT = 1;
        }
     } while (wrote_IDAT == 1);
  
     /* If there is any data left to be output, write it into a new IDAT */
     if (png_ptr->zbuf_size != png_ptr->zstream.avail_out)
     {
        /* Write the IDAT and reset the zlib output buffer */
        png_write_IDAT(png_ptr, png_ptr->zbuf,
            png_ptr->zbuf_size - png_ptr->zstream.avail_out);
     }
     png_ptr->flush_rows = 0;
     png_flush(png_ptr);
  }
  #endif /* PNG_WRITE_FLUSH_SUPPORTED */
  
  /* Free all memory used by the write */
  void PNGAPI
  png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)
  {
     png_structp png_ptr = NULL;
     png_infop info_ptr = NULL;
  #ifdef PNG_USER_MEM_SUPPORTED
     png_free_ptr free_fn = NULL;
     png_voidp mem_ptr = NULL;
  #endif
  
     png_debug(1, "in png_destroy_write_struct");
  
     if (png_ptr_ptr != NULL)
     {
        png_ptr = *png_ptr_ptr;
  #ifdef PNG_USER_MEM_SUPPORTED
        free_fn = png_ptr->free_fn;
        mem_ptr = png_ptr->mem_ptr;
  #endif
     }
  
  #ifdef PNG_USER_MEM_SUPPORTED
     if (png_ptr != NULL)
     {
        free_fn = png_ptr->free_fn;
        mem_ptr = png_ptr->mem_ptr;
     }
  #endif
  
     if (info_ptr_ptr != NULL)
        info_ptr = *info_ptr_ptr;
  
     if (info_ptr != NULL)
     {
        if (png_ptr != NULL)
        {
           png_free_data(png_ptr, info_ptr, PNG_FREE_ALL, -1);
  
  #ifdef PNG_HANDLE_AS_UNKNOWN_SUPPORTED
           if (png_ptr->num_chunk_list)
           {
              png_free(png_ptr, png_ptr->chunk_list);
              png_ptr->num_chunk_list = 0;
           }
  #endif
        }
  
  #ifdef PNG_USER_MEM_SUPPORTED
        png_destroy_struct_2((png_voidp)info_ptr, (png_free_ptr)free_fn,
            (png_voidp)mem_ptr);
  #else
        png_destroy_struct((png_voidp)info_ptr);
  #endif
        *info_ptr_ptr = NULL;
     }
  
     if (png_ptr != NULL)
     {
        png_write_destroy(png_ptr);
  #ifdef PNG_USER_MEM_SUPPORTED
        png_destroy_struct_2((png_voidp)png_ptr, (png_free_ptr)free_fn,
            (png_voidp)mem_ptr);
  #else
        png_destroy_struct((png_voidp)png_ptr);
  #endif
        *png_ptr_ptr = NULL;
     }
  }
  
  
  /* Free any memory used in png_ptr struct (old method) */
  void /* PRIVATE */
  png_write_destroy(png_structp png_ptr)
  {
  #ifdef PNG_SETJMP_SUPPORTED
     jmp_buf tmp_jmp; /* Save jump buffer */
  #endif
     png_error_ptr error_fn;
  #ifdef PNG_WARNINGS_SUPPORTED
     png_error_ptr warning_fn;
  #endif
     png_voidp error_ptr;
  #ifdef PNG_USER_MEM_SUPPORTED
     png_free_ptr free_fn;
  #endif
  
     png_debug(1, "in png_write_destroy");
  
     /* Free any memory zlib uses */
     if (png_ptr->zlib_state != PNG_ZLIB_UNINITIALIZED)
        deflateEnd(&png_ptr->zstream);
  
     /* Free our memory.  png_free checks NULL for us. */
     png_free(png_ptr, png_ptr->zbuf);
     png_free(png_ptr, png_ptr->row_buf);
  #ifdef PNG_WRITE_FILTER_SUPPORTED
     png_free(png_ptr, png_ptr->prev_row);
     png_free(png_ptr, png_ptr->sub_row);
     png_free(png_ptr, png_ptr->up_row);
     png_free(png_ptr, png_ptr->avg_row);
     png_free(png_ptr, png_ptr->paeth_row);
  #endif
  
  #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED
     /* Use this to save a little code space, it doesn't free the filter_costs */
     png_reset_filter_heuristics(png_ptr);
     png_free(png_ptr, png_ptr->filter_costs);
     png_free(png_ptr, png_ptr->inv_filter_costs);
  #endif
  
  #ifdef PNG_SETJMP_SUPPORTED
     /* Reset structure */
     png_memcpy(tmp_jmp, png_ptr->longjmp_buffer, png_sizeof(jmp_buf));
  #endif
  
     error_fn = png_ptr->error_fn;
  #ifdef PNG_WARNINGS_SUPPORTED
     warning_fn = png_ptr->warning_fn;
  #endif
     error_ptr = png_ptr->error_ptr;
  #ifdef PNG_USER_MEM_SUPPORTED
     free_fn = png_ptr->free_fn;
  #endif
  
     png_memset(png_ptr, 0, png_sizeof(png_struct));
  
     png_ptr->error_fn = error_fn;
  #ifdef PNG_WARNINGS_SUPPORTED
     png_ptr->warning_fn = warning_fn;
  #endif
     png_ptr->error_ptr = error_ptr;
  #ifdef PNG_USER_MEM_SUPPORTED
     png_ptr->free_fn = free_fn;
  #endif
  
  #ifdef PNG_SETJMP_SUPPORTED
     png_memcpy(png_ptr->longjmp_buffer, tmp_jmp, png_sizeof(jmp_buf));
  #endif
  }
  
  /* Allow the application to select one or more row filters to use. */
  void PNGAPI
  png_set_filter(png_structp png_ptr, int method, int filters)
  {
     png_debug(1, "in png_set_filter");
  
     if (png_ptr == NULL)
        return;
  
  #ifdef PNG_MNG_FEATURES_SUPPORTED
     if ((png_ptr->mng_features_permitted & PNG_FLAG_MNG_FILTER_64) &&
         (method == PNG_INTRAPIXEL_DIFFERENCING))
        method = PNG_FILTER_TYPE_BASE;
  
  #endif
     if (method == PNG_FILTER_TYPE_BASE)
     {
        switch (filters & (PNG_ALL_FILTERS | 0x07))
        {
  #ifdef PNG_WRITE_FILTER_SUPPORTED
           case 5:
           case 6:
           case 7: png_warning(png_ptr, "Unknown row filter for method 0");
  #endif /* PNG_WRITE_FILTER_SUPPORTED */
           case PNG_FILTER_VALUE_NONE:
              png_ptr->do_filter = PNG_FILTER_NONE; break;
  
  #ifdef PNG_WRITE_FILTER_SUPPORTED
           case PNG_FILTER_VALUE_SUB:
              png_ptr->do_filter = PNG_FILTER_SUB; break;
  
           case PNG_FILTER_VALUE_UP:
              png_ptr->do_filter = PNG_FILTER_UP; break;
  
           case PNG_FILTER_VALUE_AVG:
              png_ptr->do_filter = PNG_FILTER_AVG; break;
  
           case PNG_FILTER_VALUE_PAETH:
              png_ptr->do_filter = PNG_FILTER_PAETH; break;
  
           default:
              png_ptr->do_filter = (png_byte)filters; break;
  #else
           default:
              png_warning(png_ptr, "Unknown row filter for method 0");
  #endif /* PNG_WRITE_FILTER_SUPPORTED */
        }
  
        /* If we have allocated the row_buf, this means we have already started
         * with the image and we should have allocated all of the filter buffers
         * that have been selected.  If prev_row isn't already allocated, then
         * it is too late to start using the filters that need it, since we
         * will be missing the data in the previous row.  If an application
         * wants to start and stop using particular filters during compression,
         * it should start out with all of the filters, and then add and
         * remove them after the start of compression.
         */
        if (png_ptr->row_buf != NULL)
        {
  #ifdef PNG_WRITE_FILTER_SUPPORTED
           if ((png_ptr->do_filter & PNG_FILTER_SUB) && png_ptr->sub_row == NULL)
           {
              png_ptr->sub_row = (png_bytep)png_malloc(png_ptr,
                  (png_ptr->rowbytes + 1));
              png_ptr->sub_row[0] = PNG_FILTER_VALUE_SUB;
           }
  
           if ((png_ptr->do_filter & PNG_FILTER_UP) && png_ptr->up_row == NULL)
           {
              if (png_ptr->prev_row == NULL)
              {
                 png_warning(png_ptr, "Can't add Up filter after starting");
                 png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                     ~PNG_FILTER_UP);
              }
  
              else
              {
                 png_ptr->up_row = (png_bytep)png_malloc(png_ptr,
                     (png_ptr->rowbytes + 1));
                 png_ptr->up_row[0] = PNG_FILTER_VALUE_UP;
              }
           }
  
           if ((png_ptr->do_filter & PNG_FILTER_AVG) && png_ptr->avg_row == NULL)
           {
              if (png_ptr->prev_row == NULL)
              {
                 png_warning(png_ptr, "Can't add Average filter after starting");
                 png_ptr->do_filter = (png_byte)(png_ptr->do_filter &
                     ~PNG_FILTER_AVG);
              }
  
              else
              {
                 png_ptr->avg_row = (png_bytep)png_malloc(png_ptr,
                     (png_ptr->rowbytes + 1));
                 png_ptr->avg_row[0] = PNG_FILTER_VALUE_AVG;
              }
           }
  
           if ((png_ptr->do_filter & PNG_FILTER_PAETH) &&
               png_ptr->paeth_row == NULL)
           {
              if (png_ptr->prev_row == NULL)
              {
                 png_warning(png_ptr, "Can't add Paeth filter after starting");
                 png_ptr->do_filter &= (png_byte)(~PNG_FILTER_PAETH);
              }
  
              else
              {
                 png_ptr->paeth_row = (png_bytep)png_malloc(png_ptr,
                     (png_ptr->rowbytes + 1));
                 png_ptr->paeth_row[0] = PNG_FILTER_VALUE_PAETH;
              }
           }
  
           if (png_ptr->do_filter == PNG_NO_FILTERS)
  #endif /* PNG_WRITE_FILTER_SUPPORTED */
              png_ptr->do_filter = PNG_FILTER_NONE;
        }
     }
     else
        png_error(png_ptr, "Unknown custom filter method");
  }
  
  /* This allows us to influence the way in which libpng chooses the "best"
   * filter for the current scanline.  While the "minimum-sum-of-absolute-
   * differences metric is relatively fast and effective, there is some
   * question as to whether it can be improved upon by trying to keep the
   * filtered data going to zlib more consistent, hopefully resulting in
   * better compression.
   */
  #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED      /* GRR 970116 */
  /* Convenience reset API. */
  static void
  png_reset_filter_heuristics(png_structp png_ptr)
  {
     /* Clear out any old values in the 'weights' - this must be done because if
      * the app calls set_filter_heuristics multiple times with different
      * 'num_weights' values we would otherwise potentially have wrong sized
      * arrays.
      */
     png_ptr->num_prev_filters = 0;
     png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_UNWEIGHTED;
     if (png_ptr->prev_filters != NULL)
     {
        png_bytep old = png_ptr->prev_filters;
        png_ptr->prev_filters = NULL;
        png_free(png_ptr, old);
     }
     if (png_ptr->filter_weights != NULL)
     {
        png_uint_16p old = png_ptr->filter_weights;
        png_ptr->filter_weights = NULL;
        png_free(png_ptr, old);
     }
  
     if (png_ptr->inv_filter_weights != NULL)
     {
        png_uint_16p old = png_ptr->inv_filter_weights;
        png_ptr->inv_filter_weights = NULL;
        png_free(png_ptr, old);
     }
  
     /* Leave the filter_costs - this array is fixed size. */
  }
  
  static int
  png_init_filter_heuristics(png_structp png_ptr, int heuristic_method,
     int num_weights)
  {
     if (png_ptr == NULL)
        return 0;
  
     /* Clear out the arrays */
     png_reset_filter_heuristics(png_ptr);
  
     /* Check arguments; the 'reset' function makes the correct settings for the
      * unweighted case, but we must handle the weight case by initializing the
      * arrays for the caller.
      */
     if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
     {
        int i;
  
        if (num_weights > 0)
        {
           png_ptr->prev_filters = (png_bytep)png_malloc(png_ptr,
               (png_uint_32)(png_sizeof(png_byte) * num_weights));
  
           /* To make sure that the weighting starts out fairly */
           for (i = 0; i < num_weights; i++)
           {
              png_ptr->prev_filters[i] = 255;
           }
  
           png_ptr->filter_weights = (png_uint_16p)png_malloc(png_ptr,
               (png_uint_32)(png_sizeof(png_uint_16) * num_weights));
  
           png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,
               (png_uint_32)(png_sizeof(png_uint_16) * num_weights));
  
           for (i = 0; i < num_weights; i++)
           {
              png_ptr->inv_filter_weights[i] =
              png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
           }
  
           /* Safe to set this now */
           png_ptr->num_prev_filters = (png_byte)num_weights;
        }
  
        /* If, in the future, there are other filter methods, this would
         * need to be based on png_ptr->filter.
         */
        if (png_ptr->filter_costs == NULL)
        {
           png_ptr->filter_costs = (png_uint_16p)png_malloc(png_ptr,
               (png_uint_32)(png_sizeof(png_uint_16) * PNG_FILTER_VALUE_LAST));
  
           png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,
               (png_uint_32)(png_sizeof(png_uint_16) * PNG_FILTER_VALUE_LAST));
        }
  
        for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
        {
           png_ptr->inv_filter_costs[i] =
           png_ptr->filter_costs[i] = PNG_COST_FACTOR;
        }
  
        /* All the arrays are inited, safe to set this: */
        png_ptr->heuristic_method = PNG_FILTER_HEURISTIC_WEIGHTED;
  
        /* Return the 'ok' code. */
        return 1;
     }
     else if (heuristic_method == PNG_FILTER_HEURISTIC_DEFAULT ||
        heuristic_method == PNG_FILTER_HEURISTIC_UNWEIGHTED)
     {
        return 1;
     }
     else
     {
        png_warning(png_ptr, "Unknown filter heuristic method");
        return 0;
     }
  }
  
  /* Provide floating and fixed point APIs */
  #ifdef PNG_FLOATING_POINT_SUPPORTED
  void PNGAPI
  png_set_filter_heuristics(png_structp png_ptr, int heuristic_method,
      int num_weights, png_const_doublep filter_weights,
      png_const_doublep filter_costs)
  {
     png_debug(1, "in png_set_filter_heuristics");
  
     /* The internal API allocates all the arrays and ensures that the elements of
      * those arrays are set to the default value.
      */
     if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
        return;
  
     /* If using the weighted method copy in the weights. */
     if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
     {
        int i;
        for (i = 0; i < num_weights; i++)
        {
           if (filter_weights[i] <= 0.0)
           {
              png_ptr->inv_filter_weights[i] =
              png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
           }
  
           else
           {
              png_ptr->inv_filter_weights[i] =
                  (png_uint_16)(PNG_WEIGHT_FACTOR*filter_weights[i]+.5);
  
              png_ptr->filter_weights[i] =
                  (png_uint_16)(PNG_WEIGHT_FACTOR/filter_weights[i]+.5);
           }
        }
  
        /* Here is where we set the relative costs of the different filters.  We
         * should take the desired compression level into account when setting
         * the costs, so that Paeth, for instance, has a high relative cost at low
         * compression levels, while it has a lower relative cost at higher
         * compression settings.  The filter types are in order of increasing
         * relative cost, so it would be possible to do this with an algorithm.
         */
        for (i = 0; i < PNG_FILTER_VALUE_LAST; i++) if (filter_costs[i] >= 1.0)
        {
           png_ptr->inv_filter_costs[i] =
               (png_uint_16)(PNG_COST_FACTOR / filter_costs[i] + .5);
  
           png_ptr->filter_costs[i] =
               (png_uint_16)(PNG_COST_FACTOR * filter_costs[i] + .5);
        }
     }
  }
  #endif /* FLOATING_POINT */
  
  #ifdef PNG_FIXED_POINT_SUPPORTED
  void PNGAPI
  png_set_filter_heuristics_fixed(png_structp png_ptr, int heuristic_method,
      int num_weights, png_const_fixed_point_p filter_weights,
      png_const_fixed_point_p filter_costs)
  {
     png_debug(1, "in png_set_filter_heuristics_fixed");
  
     /* The internal API allocates all the arrays and ensures that the elements of
      * those arrays are set to the default value.
      */
     if (!png_init_filter_heuristics(png_ptr, heuristic_method, num_weights))
        return;
  
     /* If using the weighted method copy in the weights. */
     if (heuristic_method == PNG_FILTER_HEURISTIC_WEIGHTED)
     {
        int i;
        for (i = 0; i < num_weights; i++)
        {
           if (filter_weights[i] <= 0)
           {
              png_ptr->inv_filter_weights[i] =
              png_ptr->filter_weights[i] = PNG_WEIGHT_FACTOR;
           }
  
           else
           {
              png_ptr->inv_filter_weights[i] = (png_uint_16)
                 ((PNG_WEIGHT_FACTOR*filter_weights[i]+PNG_FP_HALF)/PNG_FP_1);
  
              png_ptr->filter_weights[i] = (png_uint_16)((PNG_WEIGHT_FACTOR*
                 PNG_FP_1+(filter_weights[i]/2))/filter_weights[i]);
           }
        }
  
        /* Here is where we set the relative costs of the different filters.  We
         * should take the desired compression level into account when setting
         * the costs, so that Paeth, for instance, has a high relative cost at low
         * compression levels, while it has a lower relative cost at higher
         * compression settings.  The filter types are in order of increasing
         * relative cost, so it would be possible to do this with an algorithm.
         */
        for (i = 0; i < PNG_FILTER_VALUE_LAST; i++)
           if (filter_costs[i] >= PNG_FP_1)
        {
           png_uint_32 tmp;
  
           /* Use a 32 bit unsigned temporary here because otherwise the
            * intermediate value will be a 32 bit *signed* integer (ANSI rules)
            * and this will get the wrong answer on division.
            */
           tmp = PNG_COST_FACTOR*PNG_FP_1 + (filter_costs[i]/2);
           tmp /= filter_costs[i];
  
           png_ptr->inv_filter_costs[i] = (png_uint_16)tmp;
  
           tmp = PNG_COST_FACTOR * filter_costs[i] + PNG_FP_HALF;
           tmp /= PNG_FP_1;
  
           png_ptr->filter_costs[i] = (png_uint_16)tmp;
        }
     }
  }
  #endif /* FIXED_POINT */
  #endif /* PNG_WRITE_WEIGHTED_FILTER_SUPPORTED */
  
  void PNGAPI
  png_set_compression_level(png_structp png_ptr, int level)
  {
     png_debug(1, "in png_set_compression_level");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_LEVEL;
     png_ptr->zlib_level = level;
  }
  
  void PNGAPI
  png_set_compression_mem_level(png_structp png_ptr, int mem_level)
  {
     png_debug(1, "in png_set_compression_mem_level");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_MEM_LEVEL;
     png_ptr->zlib_mem_level = mem_level;
  }
  
  void PNGAPI
  png_set_compression_strategy(png_structp png_ptr, int strategy)
  {
     png_debug(1, "in png_set_compression_strategy");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_STRATEGY;
     png_ptr->zlib_strategy = strategy;
  }
  
  /* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
   * smaller value of window_bits if it can do so safely.
   */
  void PNGAPI
  png_set_compression_window_bits(png_structp png_ptr, int window_bits)
  {
     if (png_ptr == NULL)
        return;
  
     if (window_bits > 15)
        png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
  
     else if (window_bits < 8)
        png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
  
  #ifndef WBITS_8_OK
     /* Avoid libpng bug with 256-byte windows */
     if (window_bits == 8)
        {
          png_warning(png_ptr, "Compression window is being reset to 512");
          window_bits = 9;
        }
  
  #endif
     png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_WINDOW_BITS;
     png_ptr->zlib_window_bits = window_bits;
  }
  
  void PNGAPI
  png_set_compression_method(png_structp png_ptr, int method)
  {
     png_debug(1, "in png_set_compression_method");
  
     if (png_ptr == NULL)
        return;
  
     if (method != 8)
        png_warning(png_ptr, "Only compression method 8 is supported by PNG");
  
     png_ptr->flags |= PNG_FLAG_ZLIB_CUSTOM_METHOD;
     png_ptr->zlib_method = method;
  }
  
  /* The following were added to libpng-1.5.4 */
  #ifdef PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED
  void PNGAPI
  png_set_text_compression_level(png_structp png_ptr, int level)
  {
     png_debug(1, "in png_set_text_compression_level");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_LEVEL;
     png_ptr->zlib_text_level = level;
  }
  
  void PNGAPI
  png_set_text_compression_mem_level(png_structp png_ptr, int mem_level)
  {
     png_debug(1, "in png_set_text_compression_mem_level");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_MEM_LEVEL;
     png_ptr->zlib_text_mem_level = mem_level;
  }
  
  void PNGAPI
  png_set_text_compression_strategy(png_structp png_ptr, int strategy)
  {
     png_debug(1, "in png_set_text_compression_strategy");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_STRATEGY;
     png_ptr->zlib_text_strategy = strategy;
  }
  
  /* If PNG_WRITE_OPTIMIZE_CMF_SUPPORTED is defined, libpng will use a
   * smaller value of window_bits if it can do so safely.
   */
  void PNGAPI
  png_set_text_compression_window_bits(png_structp png_ptr, int window_bits)
  {
     if (png_ptr == NULL)
        return;
  
     if (window_bits > 15)
        png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");
  
     else if (window_bits < 8)
        png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");
  
  #ifndef WBITS_8_OK
     /* Avoid libpng bug with 256-byte windows */
     if (window_bits == 8)
        {
          png_warning(png_ptr, "Text compression window is being reset to 512");
          window_bits = 9;
        }
  
  #endif
     png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_WINDOW_BITS;
     png_ptr->zlib_text_window_bits = window_bits;
  }
  
  void PNGAPI
  png_set_text_compression_method(png_structp png_ptr, int method)
  {
     png_debug(1, "in png_set_text_compression_method");
  
     if (png_ptr == NULL)
        return;
  
     if (method != 8)
        png_warning(png_ptr, "Only compression method 8 is supported by PNG");
  
     png_ptr->flags |= PNG_FLAG_ZTXT_CUSTOM_METHOD;
     png_ptr->zlib_text_method = method;
  }
  #endif /* PNG_WRITE_CUSTOMIZE_ZTXT_COMPRESSION_SUPPORTED */
  /* end of API added to libpng-1.5.4 */
  
  void PNGAPI
  png_set_write_status_fn(png_structp png_ptr, png_write_status_ptr write_row_fn)
  {
     if (png_ptr == NULL)
        return;
  
     png_ptr->write_row_fn = write_row_fn;
  }
  
  #ifdef PNG_WRITE_USER_TRANSFORM_SUPPORTED
  void PNGAPI
  png_set_write_user_transform_fn(png_structp png_ptr, png_user_transform_ptr
      write_user_transform_fn)
  {
     png_debug(1, "in png_set_write_user_transform_fn");
  
     if (png_ptr == NULL)
        return;
  
     png_ptr->transformations |= PNG_USER_TRANSFORM;
     png_ptr->write_user_transform_fn = write_user_transform_fn;
  }
  #endif
  
  
  #ifdef PNG_INFO_IMAGE_SUPPORTED
  void PNGAPI
  png_write_png(png_structp png_ptr, png_infop info_ptr,
      int transforms, voidp params)
  {
     if (png_ptr == NULL || info_ptr == NULL)
        return;
  
     /* Write the file header information. */
     png_write_info(png_ptr, info_ptr);
  
     /* ------ these transformations don't touch the info structure ------- */
  
  #ifdef PNG_WRITE_INVERT_SUPPORTED
     /* Invert monochrome pixels */
     if (transforms & PNG_TRANSFORM_INVERT_MONO)
        png_set_invert_mono(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_SHIFT_SUPPORTED
     /* Shift the pixels up to a legal bit depth and fill in
      * as appropriate to correctly scale the image.
      */
     if ((transforms & PNG_TRANSFORM_SHIFT)
         && (info_ptr->valid & PNG_INFO_sBIT))
        png_set_shift(png_ptr, &info_ptr->sig_bit);
  #endif
  
  #ifdef PNG_WRITE_PACK_SUPPORTED
     /* Pack pixels into bytes */
     if (transforms & PNG_TRANSFORM_PACKING)
         png_set_packing(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
     /* Swap location of alpha bytes from ARGB to RGBA */
     if (transforms & PNG_TRANSFORM_SWAP_ALPHA)
        png_set_swap_alpha(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_FILLER_SUPPORTED
     /* Pack XRGB/RGBX/ARGB/RGBA into RGB (4 channels -> 3 channels) */
     if (transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER)
        png_set_filler(png_ptr, 0, PNG_FILLER_AFTER);
  
     else if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)
        png_set_filler(png_ptr, 0, PNG_FILLER_BEFORE);
  #endif
  
  #ifdef PNG_WRITE_BGR_SUPPORTED
     /* Flip BGR pixels to RGB */
     if (transforms & PNG_TRANSFORM_BGR)
        png_set_bgr(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_SWAP_SUPPORTED
     /* Swap bytes of 16-bit files to most significant byte first */
     if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)
        png_set_swap(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_PACKSWAP_SUPPORTED
     /* Swap bits of 1, 2, 4 bit packed pixel formats */
     if (transforms & PNG_TRANSFORM_PACKSWAP)
        png_set_packswap(png_ptr);
  #endif
  
  #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
     /* Invert the alpha channel from opacity to transparency */
     if (transforms & PNG_TRANSFORM_INVERT_ALPHA)
        png_set_invert_alpha(png_ptr);
  #endif
  
     /* ----------------------- end of transformations ------------------- */
  
     /* Write the bits */
     if (info_ptr->valid & PNG_INFO_IDAT)
         png_write_image(png_ptr, info_ptr->row_pointers);
  
     /* It is REQUIRED to call this to finish writing the rest of the file */
     png_write_end(png_ptr, info_ptr);
  
     PNG_UNUSED(transforms)   /* Quiet compiler warnings */
     PNG_UNUSED(params)
  }
  #endif
  #endif /* PNG_WRITE_SUPPORTED */
  