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 /* pngwrite.c - general routines to write a PNG file

  *

  * Last changed in libpng 1.6.10 [March 6, 2014]

  * Copyright (c) 1998-2014 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"

 #if defined(PNG_SIMPLIFIED_WRITE_SUPPORTED) && defined(PNG_STDIO_SUPPORTED)

 #  include <errno.h>

 #endif

 #ifdef PNG_WRITE_SUPPORTED

 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED

 /* Write out all the unknown chunks for the current given location */

 static void

 write_unknown_chunks(png_structrp png_ptr, png_const_inforp info_ptr,

    unsigned int where)

 {

    if (info_ptr->unknown_chunks_num)

    {

       png_const_unknown_chunkp up;

       png_debug(5, "writing extra chunks");

       for (up = info_ptr->unknown_chunks;

            up < info_ptr->unknown_chunks + info_ptr->unknown_chunks_num;

            ++up)

          if (up->location & where)

       {

          /* If per-chunk unknown chunk handling is enabled use it, otherwise

           * just write the chunks the application has set.

           */

 #ifdef PNG_SET_UNKNOWN_CHUNKS_SUPPORTED

          int keep = png_handle_as_unknown(png_ptr, up->name);

          /* NOTE: this code is radically different from the read side in the

           * matter of handling an ancillary unknown chunk.  In the read side

           * the default behavior is to discard it, in the code below the default

           * behavior is to write it.  Critical chunks are, however, only

           * written if explicitly listed or if the default is set to write all

           * unknown chunks.

           *

           * The default handling is also slightly weird - it is not possible to

           * stop the writing of all unsafe-to-copy chunks!

           *

           * TODO: REVIEW: this would seem to be a bug.

           */

          if (keep != PNG_HANDLE_CHUNK_NEVER &&

              ((up->name[3] & 0x20) /* safe-to-copy overrides everything */ ||

               keep == PNG_HANDLE_CHUNK_ALWAYS ||

               (keep == PNG_HANDLE_CHUNK_AS_DEFAULT &&

                png_ptr->unknown_default == PNG_HANDLE_CHUNK_ALWAYS)))

 #endif

          {

             /* TODO: review, what is wrong with a zero length unknown chunk? */

             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_WRITE_UNKNOWN_CHUNKS_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_structrp png_ptr, png_const_inforp 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.

     *

     * 1.6.0: COLORSPACE support controls the writing of these chunks too, and

     * the chunks will be written if the WRITE routine is there and information

     * is available in the COLORSPACE.  (See png_colorspace_sync_info in png.c

     * for where the valid flags get set.)

     *

     * Under certain circumstances the colorspace can be invalidated without

     * syncing the info_struct 'valid' flags; this happens if libpng detects and

     * error and calls png_error while the color space is being set, yet the

     * application continues writing the PNG.  So check the 'invalid' flag here

     * too.

     */

 #ifdef PNG_WRITE_APNG_SUPPORTED

    if (info_ptr->valid & PNG_INFO_acTL)

       png_write_acTL(png_ptr, info_ptr->num_frames, info_ptr->num_plays);

 #endif

 #ifdef PNG_GAMMA_SUPPORTED

 #  ifdef PNG_WRITE_gAMA_SUPPORTED

       if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&

          (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) &&

          (info_ptr->valid & PNG_INFO_gAMA))

          png_write_gAMA_fixed(png_ptr, info_ptr->colorspace.gamma);

 #  endif

 #endif

 #ifdef PNG_COLORSPACE_SUPPORTED

    /* Write only one of sRGB or an ICC profile.  If a profile was supplied

     * and it matches one of the known sRGB ones issue a warning.

     */

 #  ifdef PNG_WRITE_iCCP_SUPPORTED

       if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&

          (info_ptr->valid & PNG_INFO_iCCP))

       {

 #        ifdef PNG_WRITE_sRGB_SUPPORTED

             if (info_ptr->valid & PNG_INFO_sRGB)

                png_app_warning(png_ptr,

                   "profile matches sRGB but writing iCCP instead");

 #        endif

          png_write_iCCP(png_ptr, info_ptr->iccp_name,

             info_ptr->iccp_profile);

       }

 #     ifdef PNG_WRITE_sRGB_SUPPORTED

          else

 #     endif

 #  endif

 #  ifdef PNG_WRITE_sRGB_SUPPORTED

       if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&

          (info_ptr->valid & PNG_INFO_sRGB))

          png_write_sRGB(png_ptr, info_ptr->colorspace.rendering_intent);

 #  endif /* WRITE_sRGB */

 #endif /* COLORSPACE */

 #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_COLORSPACE_SUPPORTED

 #  ifdef PNG_WRITE_cHRM_SUPPORTED

       if (!(info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) &&

          (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) &&

          (info_ptr->valid & PNG_INFO_cHRM))

          png_write_cHRM_fixed(png_ptr, &info_ptr->colorspace.end_points_xy);

 #  endif

 #endif

 #ifdef PNG_WRITE_UNKNOWN_CHUNKS_SUPPORTED

       write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_IHDR);

 #endif

       png_ptr->mode |= PNG_WROTE_INFO_BEFORE_PLTE;

    }

 }

 void PNGAPI

 png_write_info(png_structrp png_ptr, png_const_inforp 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

    write_unknown_chunks(png_ptr, info_ptr, PNG_HAVE_PLTE);

 #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_structrp png_ptr, png_inforp 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");

 #ifdef PNG_WRITE_APNG_SUPPORTED

    if (png_ptr->num_frames_written != png_ptr->num_frames_to_write)

       png_error(png_ptr, "Not enough frames written");

 #endif

 #ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED

    if (png_ptr->num_palette_max > png_ptr->num_palette)

       png_benign_error(png_ptr, "Wrote palette index exceeding num_palette");

 #endif

    /* 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

       write_unknown_chunks(png_ptr, info_ptr, PNG_AFTER_IDAT);

 #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

 void PNGAPI

 png_convert_from_struct_tm(png_timep ptime, PNG_CONST struct tm * 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)

 {

 #ifndef PNG_USER_MEM_SUPPORTED

    png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,

       error_fn, warn_fn, NULL, NULL, NULL);

 #else

    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 */

 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)

 {

    png_structrp png_ptr = png_create_png_struct(user_png_ver, error_ptr,

       error_fn, warn_fn, mem_ptr, malloc_fn, free_fn);

 #endif /* PNG_USER_MEM_SUPPORTED */

    if (png_ptr != NULL)

    {

       /* Set the zlib control values to defaults; they can be overridden by the

        * application after the struct has been created.

        */

       png_ptr->zbuffer_size = PNG_ZBUF_SIZE;

       /* The 'zlib_strategy' setting is irrelevant because png_default_claim in

        * pngwutil.c defaults it according to whether or not filters will be

        * used, and ignores this setting.

        */

       png_ptr->zlib_strategy = PNG_Z_DEFAULT_STRATEGY;

       png_ptr->zlib_level = PNG_Z_DEFAULT_COMPRESSION;

       png_ptr->zlib_mem_level = 8;

       png_ptr->zlib_window_bits = 15;

       png_ptr->zlib_method = 8;

 #ifdef PNG_WRITE_COMPRESSED_TEXT_SUPPORTED

       png_ptr->zlib_text_strategy = PNG_TEXT_Z_DEFAULT_STRATEGY;

       png_ptr->zlib_text_level = PNG_TEXT_Z_DEFAULT_COMPRESSION;

       png_ptr->zlib_text_mem_level = 8;

       png_ptr->zlib_text_window_bits = 15;

       png_ptr->zlib_text_method = 8;

 #endif /* PNG_WRITE_COMPRESSED_TEXT_SUPPORTED */

       /* This is a highly dubious configuration option; by default it is off,

        * but it may be appropriate for private builds that are testing

        * extensions not conformant to the current specification, or of

        * applications that must not fail to write at all costs!

        */

 #ifdef PNG_BENIGN_WRITE_ERRORS_SUPPORTED

       png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;

       /* In stable builds only warn if an application error can be completely

        * handled.

        */

 #endif

       /* App warnings are warnings in release (or release candidate) builds but

        * are errors during development.

        */

 #if PNG_LIBPNG_BUILD_BASE_TYPE >= PNG_LIBPNG_BUILD_RC

       png_ptr->flags |= PNG_FLAG_APP_WARNINGS_WARN;

 #endif

       /* TODO: delay this, it can be done in png_init_io() (if the app doesn't

        * do it itself) avoiding setting the default function if it is not

        * required.

        */

       png_set_write_fn(png_ptr, NULL, NULL, NULL);

    }

    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_structrp 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_structrp 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);

       }

    }

 }

 #ifdef PNG_MNG_FEATURES_SUPPORTED

 /* Performs intrapixel differencing  */

 static void

 png_do_write_intrapixel(png_row_infop row_info, png_bytep row)

 {

    png_debug(1, "in png_do_write_intrapixel");

    if ((row_info->color_type & PNG_COLOR_MASK_COLOR))

    {

       int bytes_per_pixel;

       png_uint_32 row_width = row_info->width;

       if (row_info->bit_depth == 8)

       {

          png_bytep rp;

          png_uint_32 i;

          if (row_info->color_type == PNG_COLOR_TYPE_RGB)

             bytes_per_pixel = 3;

          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

             bytes_per_pixel = 4;

          else

             return;

          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)

          {

             *(rp)     = (png_byte)((*rp       - *(rp + 1)) & 0xff);

             *(rp + 2) = (png_byte)((*(rp + 2) - *(rp + 1)) & 0xff);

          }

       }

 #ifdef PNG_WRITE_16BIT_SUPPORTED

       else if (row_info->bit_depth == 16)

       {

          png_bytep rp;

          png_uint_32 i;

          if (row_info->color_type == PNG_COLOR_TYPE_RGB)

             bytes_per_pixel = 6;

          else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)

             bytes_per_pixel = 8;

          else

             return;

          for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)

          {

             png_uint_32 s0   = (*(rp    ) << 8) | *(rp + 1);

             png_uint_32 s1   = (*(rp + 2) << 8) | *(rp + 3);

             png_uint_32 s2   = (*(rp + 4) << 8) | *(rp + 5);

             png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);

             png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);

             *(rp    ) = (png_byte)((red >> 8) & 0xff);

             *(rp + 1) = (png_byte)(red & 0xff);

             *(rp + 4) = (png_byte)((blue >> 8) & 0xff);

             *(rp + 5) = (png_byte)(blue & 0xff);

          }

       }

 #endif /* PNG_WRITE_16BIT_SUPPORTED */

    }

 }

 #endif /* PNG_MNG_FEATURES_SUPPORTED */

 /* Called by user to write a row of image data */

 void PNGAPI

 png_write_row(png_structrp png_ptr, png_const_bytep row)

 {

    /* 1.5.6: moved from png_struct to be a local structure: */

    png_row_info row_info;

    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 */

    row_info.color_type = png_ptr->color_type;

    row_info.width = png_ptr->usr_width;

    row_info.channels = png_ptr->usr_channels;

    row_info.bit_depth = png_ptr->usr_bit_depth;

    row_info.pixel_depth = (png_byte)(row_info.bit_depth * row_info.channels);

    row_info.rowbytes = PNG_ROWBYTES(row_info.pixel_depth, row_info.width);

    png_debug1(3, "row_info->color_type = %d", row_info.color_type);

    png_debug1(3, "row_info->width = %u", row_info.width);

    png_debug1(3, "row_info->channels = %d", row_info.channels);

    png_debug1(3, "row_info->bit_depth = %d", row_info.bit_depth);

    png_debug1(3, "row_info->pixel_depth = %d", row_info.pixel_depth);

    png_debug1(3, "row_info->rowbytes = %lu", (unsigned long)row_info.rowbytes);

    /* Copy user's row into buffer, leaving room for filter byte. */

    memcpy(png_ptr->row_buf + 1, row, 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(&row_info, png_ptr->row_buf + 1, png_ptr->pass);

       /* This should always get caught above, but still ... */

       if (!(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, &row_info);

 #endif

    /* At this point the row_info pixel depth must match the 'transformed' depth,

     * which is also the output depth.

     */

    if (row_info.pixel_depth != png_ptr->pixel_depth ||

       row_info.pixel_depth != png_ptr->transformed_pixel_depth)

       png_error(png_ptr, "internal write transform logic error");

 #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(&row_info, png_ptr->row_buf + 1);

    }

 #endif

 /* Added at libpng-1.5.10 */

 #ifdef PNG_WRITE_CHECK_FOR_INVALID_INDEX_SUPPORTED

    /* Check for out-of-range palette index */

    if (row_info.color_type == PNG_COLOR_TYPE_PALETTE &&

        png_ptr->num_palette_max >= 0)

       png_do_check_palette_indexes(png_ptr, &row_info);

 #endif

    /* Find a filter if necessary, filter the row and write it out. */

    png_write_find_filter(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_structrp 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_structrp png_ptr)

 {

    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;

    png_compress_IDAT(png_ptr, NULL, 0, Z_SYNC_FLUSH);

    png_ptr->flush_rows = 0;

    png_flush(png_ptr);

 }

 #endif /* PNG_WRITE_FLUSH_SUPPORTED */

 #ifdef PNG_WRITE_WEIGHTED_FILTER_SUPPORTED

 static void png_reset_filter_heuristics(png_structrp png_ptr);/* forward decl */

 #endif

 /* Free any memory used in png_ptr struct without freeing the struct itself. */

 static void

 png_write_destroy(png_structrp png_ptr)

 {

    png_debug(1, "in png_write_destroy");

    /* Free any memory zlib uses */

    if (png_ptr->flags & PNG_FLAG_ZSTREAM_INITIALIZED)

       deflateEnd(&png_ptr->zstream);

    /* Free our memory.  png_free checks NULL for us. */

    png_free_buffer_list(png_ptr, &png_ptr->zbuffer_list);

    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_SET_UNKNOWN_CHUNKS_SUPPORTED

    png_free(png_ptr, png_ptr->chunk_list);

 #endif

    /* The error handling and memory handling information is left intact at this

     * point: the jmp_buf may still have to be freed.  See png_destroy_png_struct

     * for how this happens.

     */

 }

 /* Free all memory used by the write.

  * In libpng 1.6.0 this API changed quietly to no longer accept a NULL value for

  * *png_ptr_ptr.  Prior to 1.6.0 it would accept such a value and it would free

  * the passed in info_structs but it would quietly fail to free any of the data

  * inside them.  In 1.6.0 it quietly does nothing (it has to be quiet because it

  * has no png_ptr.)

  */

 void PNGAPI

 png_destroy_write_struct(png_structpp png_ptr_ptr, png_infopp info_ptr_ptr)

 {

    png_debug(1, "in png_destroy_write_struct");

    if (png_ptr_ptr != NULL)

    {

       png_structrp png_ptr = *png_ptr_ptr;

       if (png_ptr != NULL) /* added in libpng 1.6.0 */

       {

          png_destroy_info_struct(png_ptr, info_ptr_ptr);

          *png_ptr_ptr = NULL;

          png_write_destroy(png_ptr);

          png_destroy_png_struct(png_ptr);

       }

    }

 }

 /* Allow the application to select one or more row filters to use. */

 void PNGAPI

 png_set_filter(png_structrp 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_app_error(png_ptr, "Unknown row filter for method 0");

             /* FALL THROUGH */

 #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_app_error(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_structrp 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_structrp 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)((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)((sizeof (png_uint_16)) * num_weights));

          png_ptr->inv_filter_weights = (png_uint_16p)png_malloc(png_ptr,

              (png_uint_32)((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)((sizeof (png_uint_16)) * PNG_FILTER_VALUE_LAST));

          png_ptr->inv_filter_costs = (png_uint_16p)png_malloc(png_ptr,

              (png_uint_32)((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_structrp 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_structrp 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_structrp png_ptr, int level)

 {

    png_debug(1, "in png_set_compression_level");

    if (png_ptr == NULL)

       return;

    png_ptr->zlib_level = level;

 }

 void PNGAPI

 png_set_compression_mem_level(png_structrp png_ptr, int mem_level)

 {

    png_debug(1, "in png_set_compression_mem_level");

    if (png_ptr == NULL)

       return;

    png_ptr->zlib_mem_level = mem_level;

 }

 void PNGAPI

 png_set_compression_strategy(png_structrp png_ptr, int strategy)

 {

    png_debug(1, "in png_set_compression_strategy");

    if (png_ptr == NULL)

       return;

    /* The flag setting here prevents the libpng dynamic selection of strategy.

     */

    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_structrp png_ptr, int window_bits)

 {

    if (png_ptr == NULL)

       return;

    /* Prior to 1.6.0 this would warn but then set the window_bits value, this

     * meant that negative window bits values could be selected which would cause

     * libpng to write a non-standard PNG file with raw deflate or gzip

     * compressed IDAT or ancillary chunks.  Such files can be read and there is

     * no warning on read, so this seems like a very bad idea.

     */

    if (window_bits > 15)

    {

       png_warning(png_ptr, "Only compression windows <= 32k supported by PNG");

       window_bits = 15;

    }

    else if (window_bits < 8)

    {

       png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");

       window_bits = 8;

    }

    png_ptr->zlib_window_bits = window_bits;

 }

 void PNGAPI

 png_set_compression_method(png_structrp png_ptr, int method)

 {

    png_debug(1, "in png_set_compression_method");

    if (png_ptr == NULL)

       return;

    /* This would produce an invalid PNG file if it worked, but it doesn't and

     * deflate will fault it, so it is harmless to just warn here.

     */

    if (method != 8)

       png_warning(png_ptr, "Only compression method 8 is supported by PNG");

    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_structrp png_ptr, int level)

 {

    png_debug(1, "in png_set_text_compression_level");

    if (png_ptr == NULL)

       return;

    png_ptr->zlib_text_level = level;

 }

 void PNGAPI

 png_set_text_compression_mem_level(png_structrp png_ptr, int mem_level)

 {

    png_debug(1, "in png_set_text_compression_mem_level");

    if (png_ptr == NULL)

       return;

    png_ptr->zlib_text_mem_level = mem_level;

 }

 void PNGAPI

 png_set_text_compression_strategy(png_structrp png_ptr, int strategy)

 {

    png_debug(1, "in png_set_text_compression_strategy");

    if (png_ptr == NULL)

       return;

    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_structrp 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");

       window_bits = 15;

    }

    else if (window_bits < 8)

    {

       png_warning(png_ptr, "Only compression windows >= 256 supported by PNG");

       window_bits = 8;

    }

    png_ptr->zlib_text_window_bits = window_bits;

 }

 void PNGAPI

 png_set_text_compression_method(png_structrp 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->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_structrp 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_structrp 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_structrp png_ptr, png_inforp info_ptr,

     int transforms, voidp params)

 {

    if (png_ptr == NULL || info_ptr == NULL)

       return;

    if ((info_ptr->valid & PNG_INFO_IDAT) == 0)

    {

       png_app_error(png_ptr, "no rows for png_write_image to write");

       return;

    }

    /* Write the file header information. */

    png_write_info(png_ptr, info_ptr);

    /* ------ these transformations don't touch the info structure ------- */

    /* Invert monochrome pixels */

    if (transforms & PNG_TRANSFORM_INVERT_MONO)

 #ifdef PNG_WRITE_INVERT_SUPPORTED

       png_set_invert_mono(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_MONO not supported");

 #endif

    /* Shift the pixels up to a legal bit depth and fill in

     * as appropriate to correctly scale the image.

     */

    if (transforms & PNG_TRANSFORM_SHIFT)

 #ifdef PNG_WRITE_SHIFT_SUPPORTED

       if (info_ptr->valid & PNG_INFO_sBIT)

          png_set_shift(png_ptr, &info_ptr->sig_bit);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_SHIFT not supported");

 #endif

    /* Pack pixels into bytes */

    if (transforms & PNG_TRANSFORM_PACKING)

 #ifdef PNG_WRITE_PACK_SUPPORTED

       png_set_packing(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_PACKING not supported");

 #endif

    /* Swap location of alpha bytes from ARGB to RGBA */

    if (transforms & PNG_TRANSFORM_SWAP_ALPHA)

 #ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED

       png_set_swap_alpha(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ALPHA not supported");

 #endif

    /* Remove a filler (X) from XRGB/RGBX/AG/GA into to convert it into

     * RGB, note that the code expects the input color type to be G or RGB; no

     * alpha channel.

     */

    if (transforms &

       (PNG_TRANSFORM_STRIP_FILLER_AFTER|PNG_TRANSFORM_STRIP_FILLER_BEFORE))

    {

 #ifdef PNG_WRITE_FILLER_SUPPORTED

       if (transforms & PNG_TRANSFORM_STRIP_FILLER_AFTER)

       {

          if (transforms & PNG_TRANSFORM_STRIP_FILLER_BEFORE)

             png_app_error(png_ptr,

                "PNG_TRANSFORM_STRIP_FILLER: BEFORE+AFTER not supported");

          /* Continue if ignored - this is the pre-1.6.10 behavior */

          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);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_STRIP_FILLER not supported");

 #endif

    }

    /* Flip BGR pixels to RGB */

    if (transforms & PNG_TRANSFORM_BGR)

 #ifdef PNG_WRITE_BGR_SUPPORTED

       png_set_bgr(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_BGR not supported");

 #endif

    /* Swap bytes of 16-bit files to most significant byte first */

    if (transforms & PNG_TRANSFORM_SWAP_ENDIAN)

 #ifdef PNG_WRITE_SWAP_SUPPORTED

       png_set_swap(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_SWAP_ENDIAN not supported");

 #endif

    /* Swap bits of 1, 2, 4 bit packed pixel formats */

    if (transforms & PNG_TRANSFORM_PACKSWAP)

 #ifdef PNG_WRITE_PACKSWAP_SUPPORTED

       png_set_packswap(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_PACKSWAP not supported");

 #endif

    /* Invert the alpha channel from opacity to transparency */

    if (transforms & PNG_TRANSFORM_INVERT_ALPHA)

 #ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED

       png_set_invert_alpha(png_ptr);

 #else

       png_app_error(png_ptr, "PNG_TRANSFORM_INVERT_ALPHA not supported");

 #endif

    /* ----------------------- end of transformations ------------------- */

    /* Write the bits */

    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(params)

 }

 #endif

 #ifdef PNG_SIMPLIFIED_WRITE_SUPPORTED

 #ifdef PNG_STDIO_SUPPORTED /* currently required for png_image_write_* */

 /* Initialize the write structure - general purpose utility. */

 static int

 png_image_write_init(png_imagep image)

 {

    png_structp png_ptr = png_create_write_struct(PNG_LIBPNG_VER_STRING, image,

           png_safe_error, png_safe_warning);

    if (png_ptr != NULL)

    {

       png_infop info_ptr = png_create_info_struct(png_ptr);

       if (info_ptr != NULL)

       {

          png_controlp control = png_voidcast(png_controlp,

             png_malloc_warn(png_ptr, (sizeof *control)));

          if (control != NULL)

          {

             memset(control, 0, (sizeof *control));

             control->png_ptr = png_ptr;

             control->info_ptr = info_ptr;

             control->for_write = 1;

             image->opaque = control;

             return 1;

          }

          /* Error clean up */

          png_destroy_info_struct(png_ptr, &info_ptr);

       }

       png_destroy_write_struct(&png_ptr, NULL);

    }

    return png_image_error(image, "png_image_write_: out of memory");

 }

 /* Arguments to png_image_write_main: */

 typedef struct

 {

    /* Arguments: */

    png_imagep      image;

    png_const_voidp buffer;

    png_int_32      row_stride;

    png_const_voidp colormap;

    int             convert_to_8bit;

    /* Local variables: */

    png_const_voidp first_row;

    ptrdiff_t       row_bytes;

    png_voidp       local_row;

 } png_image_write_control;

 /* Write png_uint_16 input to a 16-bit PNG; the png_ptr has already been set to

  * do any necessary byte swapping.  The component order is defined by the

  * png_image format value.

  */

 static int

 png_write_image_16bit(png_voidp argument)

 {

    png_image_write_control *display = png_voidcast(png_image_write_control*,

       argument);

    png_imagep image = display->image;

    png_structrp png_ptr = image->opaque->png_ptr;

    png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,

       display->first_row);

    png_uint_16p output_row = png_voidcast(png_uint_16p, display->local_row);

    png_uint_16p row_end;

    const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;

    int aindex = 0;

    png_uint_32 y = image->height;

    if (image->format & PNG_FORMAT_FLAG_ALPHA)

    {

 #     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED

          if (image->format & PNG_FORMAT_FLAG_AFIRST)

          {

             aindex = -1;

             ++input_row; /* To point to the first component */

             ++output_row;

          }

          else

 #     endif

          aindex = channels;

    }

    else

       png_error(png_ptr, "png_write_image: internal call error");

    /* Work out the output row end and count over this, note that the increment

     * above to 'row' means that row_end can actually be beyond the end of the

     * row; this is correct.

     */

    row_end = output_row + image->width * (channels+1);

    while (y-- > 0)

    {

       png_const_uint_16p in_ptr = input_row;

       png_uint_16p out_ptr = output_row;

       while (out_ptr < row_end)

       {

          const png_uint_16 alpha = in_ptr[aindex];

          png_uint_32 reciprocal = 0;

          int c;

          out_ptr[aindex] = alpha;

          /* Calculate a reciprocal.  The correct calculation is simply

           * component/alpha*65535 << 15. (I.e. 15 bits of precision); this

           * allows correct rounding by adding .5 before the shift.  'reciprocal'

           * is only initialized when required.

           */

          if (alpha > 0 && alpha < 65535)

             reciprocal = ((0xffff<<15)+(alpha>>1))/alpha;

          c = channels;

          do /* always at least one channel */

          {

             png_uint_16 component = *in_ptr++;

             /* The following gives 65535 for an alpha of 0, which is fine,

              * otherwise if 0/0 is represented as some other value there is more

              * likely to be a discontinuity which will probably damage

              * compression when moving from a fully transparent area to a

              * nearly transparent one.  (The assumption here is that opaque

              * areas tend not to be 0 intensity.)

              */

             if (component >= alpha)

                component = 65535;

             /* component<alpha, so component/alpha is less than one and

              * component*reciprocal is less than 2^31.

              */

             else if (component > 0 && alpha < 65535)

             {

                png_uint_32 calc = component * reciprocal;

                calc += 16384; /* round to nearest */

                component = (png_uint_16)(calc >> 15);

             }

             *out_ptr++ = component;

          }

          while (--c > 0);

          /* Skip to next component (skip the intervening alpha channel) */

          ++in_ptr;

          ++out_ptr;

       }

       png_write_row(png_ptr, png_voidcast(png_const_bytep, display->local_row));

       input_row += display->row_bytes/(sizeof (png_uint_16));

    }

    return 1;

 }

 /* Given 16-bit input (1 to 4 channels) write 8-bit output.  If an alpha channel

  * is present it must be removed from the components, the components are then

  * written in sRGB encoding.  No components are added or removed.

  *

  * Calculate an alpha reciprocal to reverse pre-multiplication.  As above the

  * calculation can be done to 15 bits of accuracy; however, the output needs to

  * be scaled in the range 0..255*65535, so include that scaling here.

  */

 #define UNP_RECIPROCAL(alpha) ((((0xffff*0xff)<<7)+(alpha>>1))/alpha)

 static png_byte

 png_unpremultiply(png_uint_32 component, png_uint_32 alpha,

    png_uint_32 reciprocal/*from the above macro*/)

 {

    /* The following gives 1.0 for an alpha of 0, which is fine, otherwise if 0/0

     * is represented as some other value there is more likely to be a

     * discontinuity which will probably damage compression when moving from a

     * fully transparent area to a nearly transparent one.  (The assumption here

     * is that opaque areas tend not to be 0 intensity.)

     *

     * There is a rounding problem here; if alpha is less than 128 it will end up

     * as 0 when scaled to 8 bits.  To avoid introducing spurious colors into the

     * output change for this too.

     */

    if (component >= alpha || alpha < 128)

       return 255;

    /* component<alpha, so component/alpha is less than one and

     * component*reciprocal is less than 2^31.

     */

    else if (component > 0)

    {

       /* The test is that alpha/257 (rounded) is less than 255, the first value

        * that becomes 255 is 65407.

        * NOTE: this must agree with the PNG_DIV257 macro (which must, therefore,

        * be exact!)  [Could also test reciprocal != 0]

        */

       if (alpha < 65407)

       {

          component *= reciprocal;

          component += 64; /* round to nearest */

          component >>= 7;

       }

       else

          component *= 255;

       /* Convert the component to sRGB. */

       return (png_byte)PNG_sRGB_FROM_LINEAR(component);

    }

    else

       return 0;

 }

 static int

 png_write_image_8bit(png_voidp argument)

 {

    png_image_write_control *display = png_voidcast(png_image_write_control*,

       argument);

    png_imagep image = display->image;

    png_structrp png_ptr = image->opaque->png_ptr;

    png_const_uint_16p input_row = png_voidcast(png_const_uint_16p,

       display->first_row);

    png_bytep output_row = png_voidcast(png_bytep, display->local_row);

    png_uint_32 y = image->height;

    const int channels = (image->format & PNG_FORMAT_FLAG_COLOR) ? 3 : 1;

    if (image->format & PNG_FORMAT_FLAG_ALPHA)

    {

       png_bytep row_end;

       int aindex;

 #     ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED

          if (image->format & PNG_FORMAT_FLAG_AFIRST)

          {

             aindex = -1;

             ++input_row; /* To point to the first component */

             ++output_row;

          }

          else

 #     endif

          aindex = channels;

       /* Use row_end in place of a loop counter: */

       row_end = output_row + image->width * (channels+1);

       while (y-- > 0)

       {

          png_const_uint_16p in_ptr = input_row;

          png_bytep out_ptr = output_row;

          while (out_ptr < row_end)

          {

             png_uint_16 alpha = in_ptr[aindex];

             png_byte alphabyte = (png_byte)PNG_DIV257(alpha);

             png_uint_32 reciprocal = 0;

             int c;

             /* Scale and write the alpha channel. */

             out_ptr[aindex] = alphabyte;

             if (alphabyte > 0 && alphabyte < 255)

                reciprocal = UNP_RECIPROCAL(alpha);

             c = channels;

             do /* always at least one channel */

                *out_ptr++ = png_unpremultiply(*in_ptr++, alpha, reciprocal);

             while (--c > 0);

             /* Skip to next component (skip the intervening alpha channel) */

             ++in_ptr;

             ++out_ptr;

          } /* while out_ptr < row_end */

          png_write_row(png_ptr, png_voidcast(png_const_bytep,

             display->local_row));

          input_row += display->row_bytes/(sizeof (png_uint_16));

       } /* while y */

    }

    else

    {

       /* No alpha channel, so the row_end really is the end of the row and it

        * is sufficient to loop over the components one by one.

        */

       png_bytep row_end = output_row + image->width * channels;

       while (y-- > 0)

       {

          png_const_uint_16p in_ptr = input_row;

          png_bytep out_ptr = output_row;

          while (out_ptr < row_end)

          {

             png_uint_32 component = *in_ptr++;

             component *= 255;

             *out_ptr++ = (png_byte)PNG_sRGB_FROM_LINEAR(component);

          }

          png_write_row(png_ptr, output_row);

          input_row += display->row_bytes/(sizeof (png_uint_16));

       }

    }

    return 1;

 }

 static void

 png_image_set_PLTE(png_image_write_control *display)

 {

    const png_imagep image = display->image;

    const void *cmap = display->colormap;

    const int entries = image->colormap_entries > 256 ? 256 :

       (int)image->colormap_entries;

    /* NOTE: the caller must check for cmap != NULL and entries != 0 */

    const png_uint_32 format = image->format;

    const int channels = PNG_IMAGE_SAMPLE_CHANNELS(format);

 #  if defined(PNG_FORMAT_BGR_SUPPORTED) &&\

       defined(PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED)

       const int afirst = (format & PNG_FORMAT_FLAG_AFIRST) != 0 &&

          (format & PNG_FORMAT_FLAG_ALPHA) != 0;

 #  else

 #     define afirst 0

 #  endif

 #  ifdef PNG_FORMAT_BGR_SUPPORTED

       const int bgr = (format & PNG_FORMAT_FLAG_BGR) ? 2 : 0;

 #  else

 #     define bgr 0

 #  endif

    int i, num_trans;

    png_color palette[256];

    png_byte tRNS[256];

    memset(tRNS, 255, (sizeof tRNS));

    memset(palette, 0, (sizeof palette));

    for (i=num_trans=0; i<entries; ++i)

    {

       /* This gets automatically converted to sRGB with reversal of the

        * pre-multiplication if the color-map has an alpha channel.

        */

       if (format & PNG_FORMAT_FLAG_LINEAR)

       {

          png_const_uint_16p entry = png_voidcast(png_const_uint_16p, cmap);

          entry += i * channels;

          if (channels & 1) /* no alpha */

          {

             if (channels >= 3) /* RGB */

             {

                palette[i].blue = (png_byte)PNG_sRGB_FROM_LINEAR(255 *

                   entry[(2 ^ bgr)]);

                palette[i].green = (png_byte)PNG_sRGB_FROM_LINEAR(255 *

                   entry[1]);

                palette[i].red = (png_byte)PNG_sRGB_FROM_LINEAR(255 *

                   entry[bgr]);

             }

             else /* Gray */

                palette[i].blue = palette[i].red = palette[i].green =

                   (png_byte)PNG_sRGB_FROM_LINEAR(255 * *entry);

          }

          else /* alpha */

          {

             png_uint_16 alpha = entry[afirst ? 0 : channels-1];

             png_byte alphabyte = (png_byte)PNG_DIV257(alpha);

             png_uint_32 reciprocal = 0;

             /* Calculate a reciprocal, as in the png_write_image_8bit code above

              * this is designed to produce a value scaled to 255*65535 when

              * divided by 128 (i.e. asr 7).

              */

             if (alphabyte > 0 && alphabyte < 255)

                reciprocal = (((0xffff*0xff)<<7)+(alpha>>1))/alpha;

             tRNS[i] = alphabyte;

             if (alphabyte < 255)

                num_trans = i+1;

             if (channels >= 3) /* RGB */

             {

                palette[i].blue = png_unpremultiply(entry[afirst + (2 ^ bgr)],

                   alpha, reciprocal);

                palette[i].green = png_unpremultiply(entry[afirst + 1], alpha,

                   reciprocal);

                palette[i].red = png_unpremultiply(entry[afirst + bgr], alpha,

                   reciprocal);

             }

             else /* gray */

                palette[i].blue = palette[i].red = palette[i].green =

                   png_unpremultiply(entry[afirst], alpha, reciprocal);

          }

       }

       else /* Color-map has sRGB values */

       {

          png_const_bytep entry = png_voidcast(png_const_bytep, cmap);

          entry += i * channels;

          switch (channels)

          {

             case 4:

                tRNS[i] = entry[afirst ? 0 : 3];

                if (tRNS[i] < 255)

                   num_trans = i+1;

                /* FALL THROUGH */

             case 3:

                palette[i].blue = entry[afirst + (2 ^ bgr)];

                palette[i].green = entry[afirst + 1];

                palette[i].red = entry[afirst + bgr];

                break;

             case 2:

                tRNS[i] = entry[1 ^ afirst];

                if (tRNS[i] < 255)

                   num_trans = i+1;

                /* FALL THROUGH */

             case 1:

                palette[i].blue = palette[i].red = palette[i].green =

                   entry[afirst];

                break;

             default:

                break;

          }

       }

    }

 #  ifdef afirst

 #     undef afirst

 #  endif

 #  ifdef bgr

 #     undef bgr

 #  endif

    png_set_PLTE(image->opaque->png_ptr, image->opaque->info_ptr, palette,

       entries);

    if (num_trans > 0)

       png_set_tRNS(image->opaque->png_ptr, image->opaque->info_ptr, tRNS,

          num_trans, NULL);

    image->colormap_entries = entries;

 }

 static int

 png_image_write_main(png_voidp argument)

 {

    png_image_write_control *display = png_voidcast(png_image_write_control*,

       argument);

    png_imagep image = display->image;

    png_structrp png_ptr = image->opaque->png_ptr;

    png_inforp info_ptr = image->opaque->info_ptr;

    png_uint_32 format = image->format;

    int colormap = (format & PNG_FORMAT_FLAG_COLORMAP) != 0;

    int linear = !colormap && (format & PNG_FORMAT_FLAG_LINEAR) != 0; /* input */

    int alpha = !colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0;

    int write_16bit = linear && !colormap && !display->convert_to_8bit;

 #  ifdef PNG_BENIGN_ERRORS_SUPPORTED

       /* Make sure we error out on any bad situation */

       png_set_benign_errors(png_ptr, 0/*error*/);

 #  endif

    /* Default the 'row_stride' parameter if required. */

    if (display->row_stride == 0)

       display->row_stride = PNG_IMAGE_ROW_STRIDE(*image);

    /* Set the required transforms then write the rows in the correct order. */

    if (format & PNG_FORMAT_FLAG_COLORMAP)

    {

       if (display->colormap != NULL && image->colormap_entries > 0)

       {

          png_uint_32 entries = image->colormap_entries;

          png_set_IHDR(png_ptr, info_ptr, image->width, image->height,

             entries > 16 ? 8 : (entries > 4 ? 4 : (entries > 2 ? 2 : 1)),

             PNG_COLOR_TYPE_PALETTE, PNG_INTERLACE_NONE,

             PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

          png_image_set_PLTE(display);

       }

       else

          png_error(image->opaque->png_ptr,

             "no color-map for color-mapped image");

    }

    else

       png_set_IHDR(png_ptr, info_ptr, image->width, image->height,

          write_16bit ? 16 : 8,

          ((format & PNG_FORMAT_FLAG_COLOR) ? PNG_COLOR_MASK_COLOR : 0) +

          ((format & PNG_FORMAT_FLAG_ALPHA) ? PNG_COLOR_MASK_ALPHA : 0),

          PNG_INTERLACE_NONE, PNG_COMPRESSION_TYPE_BASE, PNG_FILTER_TYPE_BASE);

    /* Counter-intuitively the data transformations must be called *after*

     * png_write_info, not before as in the read code, but the 'set' functions

     * must still be called before.  Just set the color space information, never

     * write an interlaced image.

     */

    if (write_16bit)

    {

       /* The gamma here is 1.0 (linear) and the cHRM chunk matches sRGB. */

       png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_LINEAR);

       if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))

          png_set_cHRM_fixed(png_ptr, info_ptr,

             /* color      x       y */

             /* white */ 31270, 32900,

             /* red   */ 64000, 33000,

             /* green */ 30000, 60000,

             /* blue  */ 15000,  6000

          );

    }

    else if (!(image->flags & PNG_IMAGE_FLAG_COLORSPACE_NOT_sRGB))

       png_set_sRGB(png_ptr, info_ptr, PNG_sRGB_INTENT_PERCEPTUAL);

    /* Else writing an 8-bit file and the *colors* aren't sRGB, but the 8-bit

     * space must still be gamma encoded.

     */

    else

       png_set_gAMA_fixed(png_ptr, info_ptr, PNG_GAMMA_sRGB_INVERSE);

    /* Write the file header. */

    png_write_info(png_ptr, info_ptr);

    /* Now set up the data transformations (*after* the header is written),

     * remove the handled transformations from the 'format' flags for checking.

     *

     * First check for a little endian system if writing 16 bit files.

     */

    if (write_16bit)

    {

       PNG_CONST png_uint_16 le = 0x0001;

       if (*(png_const_bytep)&le)

          png_set_swap(png_ptr);

    }

 #  ifdef PNG_SIMPLIFIED_WRITE_BGR_SUPPORTED

       if (format & PNG_FORMAT_FLAG_BGR)

       {

          if (!colormap && (format & PNG_FORMAT_FLAG_COLOR) != 0)

             png_set_bgr(png_ptr);

          format &= ~PNG_FORMAT_FLAG_BGR;

       }

 #  endif

 #  ifdef PNG_SIMPLIFIED_WRITE_AFIRST_SUPPORTED

       if (format & PNG_FORMAT_FLAG_AFIRST)

       {

          if (!colormap && (format & PNG_FORMAT_FLAG_ALPHA) != 0)

             png_set_swap_alpha(png_ptr);

          format &= ~PNG_FORMAT_FLAG_AFIRST;

       }

 #  endif

    /* If there are 16 or fewer color-map entries we wrote a lower bit depth

     * above, but the application data is still byte packed.

     */

    if (colormap && image->colormap_entries <= 16)

       png_set_packing(png_ptr);

    /* That should have handled all (both) the transforms. */

    if ((format & ~(png_uint_32)(PNG_FORMAT_FLAG_COLOR | PNG_FORMAT_FLAG_LINEAR |

          PNG_FORMAT_FLAG_ALPHA | PNG_FORMAT_FLAG_COLORMAP)) != 0)

       png_error(png_ptr, "png_write_image: unsupported transformation");

    {

       png_const_bytep row = png_voidcast(png_const_bytep, display->buffer);

       ptrdiff_t row_bytes = display->row_stride;

       if (linear)

          row_bytes *= (sizeof (png_uint_16));

       if (row_bytes < 0)

          row += (image->height-1) * (-row_bytes);

       display->first_row = row;

       display->row_bytes = row_bytes;

    }

    /* Apply 'fast' options if the flag is set. */

    if ((image->flags & PNG_IMAGE_FLAG_FAST) != 0)

    {

       png_set_filter(png_ptr, PNG_FILTER_TYPE_BASE, PNG_NO_FILTERS);

       /* NOTE: determined by experiment using pngstest, this reflects some

        * balance between the time to write the image once and the time to read

        * it about 50 times.  The speed-up in pngstest was about 10-20% of the

        * total (user) time on a heavily loaded system.

        */

       png_set_compression_level(png_ptr, 3);

    }

    /* Check for the cases that currently require a pre-transform on the row

     * before it is written.  This only applies when the input is 16-bit and

     * either there is an alpha channel or it is converted to 8-bit.

     */

    if ((linear && alpha) || (!colormap && display->convert_to_8bit))

    {

       png_bytep row = png_voidcast(png_bytep, png_malloc(png_ptr,

          png_get_rowbytes(png_ptr, info_ptr)));

       int result;

       display->local_row = row;

       if (write_16bit)

          result = png_safe_execute(image, png_write_image_16bit, display);

       else

          result = png_safe_execute(image, png_write_image_8bit, display);

       display->local_row = NULL;

       png_free(png_ptr, row);

       /* Skip the 'write_end' on error: */

       if (!result)

          return 0;

    }

    /* Otherwise this is the case where the input is in a format currently

     * supported by the rest of the libpng write code; call it directly.

     */

    else

    {

       png_const_bytep row = png_voidcast(png_const_bytep, display->first_row);

       ptrdiff_t row_bytes = display->row_bytes;

       png_uint_32 y = image->height;

       while (y-- > 0)

       {

          png_write_row(png_ptr, row);

          row += row_bytes;

       }

    }

    png_write_end(png_ptr, info_ptr);

    return 1;

 }

 int PNGAPI

 png_image_write_to_stdio(png_imagep image, FILE *file, int convert_to_8bit,

    const void *buffer, png_int_32 row_stride, const void *colormap)

 {

    /* Write the image to the given (FILE*). */

    if (image != NULL && image->version == PNG_IMAGE_VERSION)

    {

       if (file != NULL)

       {

          if (png_image_write_init(image))

          {

             png_image_write_control display;

             int result;

             /* This is slightly evil, but png_init_io doesn't do anything other

              * than this and we haven't changed the standard IO functions so

              * this saves a 'safe' function.

              */

             image->opaque->png_ptr->io_ptr = file;

             memset(&display, 0, (sizeof display));

             display.image = image;

             display.buffer = buffer;

             display.row_stride = row_stride;

             display.colormap = colormap;

             display.convert_to_8bit = convert_to_8bit;

             result = png_safe_execute(image, png_image_write_main, &display);

             png_image_free(image);

             return result;

          }

          else

             return 0;

       }

       else

          return png_image_error(image,

             "png_image_write_to_stdio: invalid argument");

    }

    else if (image != NULL)

       return png_image_error(image,

          "png_image_write_to_stdio: incorrect PNG_IMAGE_VERSION");

    else

       return 0;

 }

 int PNGAPI

 png_image_write_to_file(png_imagep image, const char *file_name,

    int convert_to_8bit, const void *buffer, png_int_32 row_stride,

    const void *colormap)

 {

    /* Write the image to the named file. */

    if (image != NULL && image->version == PNG_IMAGE_VERSION)

    {

       if (file_name != NULL)

       {

          FILE *fp = fopen(file_name, "wb");

          if (fp != NULL)

          {

             if (png_image_write_to_stdio(image, fp, convert_to_8bit, buffer,

                row_stride, colormap))

             {

                int error; /* from fflush/fclose */

                /* Make sure the file is flushed correctly. */

                if (fflush(fp) == 0 && ferror(fp) == 0)

                {

                   if (fclose(fp) == 0)

                      return 1;

                   error = errno; /* from fclose */

                }

                else

                {

                   error = errno; /* from fflush or ferror */

                   (void)fclose(fp);

                }

                (void)remove(file_name);

                /* The image has already been cleaned up; this is just used to

                 * set the error (because the original write succeeded).

                 */

                return png_image_error(image, strerror(error));

             }

             else

             {

                /* Clean up: just the opened file. */

                (void)fclose(fp);

                (void)remove(file_name);

                return 0;

             }

          }

          else

             return png_image_error(image, strerror(errno));

       }

       else

          return png_image_error(image,

             "png_image_write_to_file: invalid argument");

    }

    else if (image != NULL)

       return png_image_error(image,

          "png_image_write_to_file: incorrect PNG_IMAGE_VERSION");

    else

       return 0;

 }

 #endif /* PNG_STDIO_SUPPORTED */

 #endif /* SIMPLIFIED_WRITE */

 #ifdef PNG_WRITE_APNG_SUPPORTED

 void PNGAPI

 png_write_frame_head(png_structp png_ptr, png_infop info_ptr,

     png_bytepp row_pointers, png_uint_32 width, png_uint_32 height,

     png_uint_32 x_offset, png_uint_32 y_offset,

     png_uint_16 delay_num, png_uint_16 delay_den, png_byte dispose_op,

     png_byte blend_op)

 {

     png_debug(1, "in png_write_frame_head");

     /* there is a chance this has been set after png_write_info was called,

     * so it would be set but not written. is there a way to be sure? */

     if (!(info_ptr->valid & PNG_INFO_acTL))

         png_error(png_ptr, "png_write_frame_head(): acTL not set");

     png_write_reset(png_ptr);

     png_write_reinit(png_ptr, info_ptr, width, height);

     if ( !(png_ptr->num_frames_written == 0 &&

            (png_ptr->apng_flags & PNG_FIRST_FRAME_HIDDEN) ) )

         png_write_fcTL(png_ptr, width, height, x_offset, y_offset,

                        delay_num, delay_den, dispose_op, blend_op);

     PNG_UNUSED(row_pointers)

 }

 void PNGAPI

 png_write_frame_tail(png_structp png_ptr, png_infop info_ptr)

 {

     png_debug(1, "in png_write_frame_tail");

     png_ptr->num_frames_written++;

     PNG_UNUSED(info_ptr)

 }

 #endif /* PNG_WRITE_APNG_SUPPORTED */

 #endif /* PNG_WRITE_SUPPORTED */