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

 *

 * Last changed in libpng 1.6.19 [November 12, 2015]

 * Copyright (c) 1998-2002,2004,2006-2015 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></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 != 0)

   {

      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) != 0)

      {

         /* 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 /* WRITE_UNKNOWN_CHUNKS */

/* 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) == 0)

   {

      /* Write PNG signature */

      png_write_sig(png_ptr);

#ifdef PNG_MNG_FEATURES_SUPPORTED

      if ((png_ptr->mode & PNG_HAVE_PNG_SIGNATURE) != 0 && \

          png_ptr->mng_features_permitted != 0)

      {

         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

       * an 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_GAMMA_SUPPORTED

#  ifdef PNG_WRITE_gAMA_SUPPORTED

      if ((info_ptr->colorspace.flags & PNG_COLORSPACE_INVALID) == 0 &&

          (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_gAMA) != 0 &&

          (info_ptr->valid & PNG_INFO_gAMA) != 0)

         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) == 0 &&

             (info_ptr->valid & PNG_INFO_iCCP) != 0)

         {

#    ifdef PNG_WRITE_sRGB_SUPPORTED

               if ((info_ptr->valid & PNG_INFO_sRGB) != 0)

                  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) == 0 &&

             (info_ptr->valid & PNG_INFO_sRGB) != 0)

            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) != 0)

            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) == 0 &&

             (info_ptr->colorspace.flags & PNG_COLORSPACE_FROM_cHRM) != 0 &&

             (info_ptr->valid & PNG_INFO_cHRM) != 0)

            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) != 0)

      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) !=0)

   {

#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED

      /* Invert the alpha channel (in tRNS) */

      if ((png_ptr->transformations & PNG_INVERT_ALPHA) != 0 &&

          info_ptr->color_type == PNG_COLOR_TYPE_PALETTE)

      {

         int j, jend;

         jend = info_ptr->num_trans;

         if (jend > PNG_MAX_PALETTE_LENGTH)

            jend = PNG_MAX_PALETTE_LENGTH;

         for (j = 0; 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) != 0)

      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) != 0)

      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) != 0)

      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) != 0)

      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) != 0)

      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) != 0)

      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) != 0)

   {

      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) != 0)

      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);

         /* Mark this chunk as written */

         if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)

            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;

         else

            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;

#else

         png_warning(png_ptr, "Unable to write international text");

#endif

      }

      /* 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, info_ptr->text[i].compression);

         /* Mark this chunk as written */

         info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;

#else

         png_warning(png_ptr, "Unable to write compressed text");

#endif

      }

      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) == 0)

      png_error(png_ptr, "No IDATs written into file");

#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) != 0 &&

          (png_ptr->mode & PNG_WROTE_tIME) == 0)

         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);

            /* Mark this chunk as written */

            if (info_ptr->text[i].compression == PNG_TEXT_COMPRESSION_NONE)

               info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_NONE_WR;

            else

               info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;

#else

            png_warning(png_ptr, "Unable to write international text");

#endif

         }

         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, info_ptr->text[i].compression);

            /* Mark this chunk as written */

            info_ptr->text[i].compression = PNG_TEXT_COMPRESSION_zTXt_WR;

#else

            png_warning(png_ptr, "Unable to write compressed text");

#endif

         }

         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

            png_warning(png_ptr, "Unable to write uncompressed text");

#endif

         }

      }

#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 /* USER_MEM */

   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 /* WRITE_COMPRESSED_TEXT */

      /* 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

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

       * handled.

       */

      png_ptr->flags |= PNG_FLAG_BENIGN_ERRORS_WARN;

#endif

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

       * are errors during development.

       */

#if PNG_RELEASE_BUILD

      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) != 0)

   {

      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));

            *(rp + 2) = (png_byte)(*(rp + 2) - *(rp + 1));

         }

      }

#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);

            *(rp + 1) = (png_byte)red;

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

            *(rp + 5) = (png_byte)blue;

         }

      }

#endif /* WRITE_16BIT */

   }

}

#endif /* MNG_FEATURES */

/* 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) == 0)

         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) != 0)

         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) != 0)

         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) != 0)

         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) != 0)

         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) != 0)

         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) != 0)

         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) != 0)

         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 != 0 &&

       (png_ptr->transformations & PNG_INTERLACE) != 0)

   {

      switch (png_ptr->pass)

      {

         case 0:

            if ((png_ptr->row_number & 0x07) != 0)

            {

               png_write_finish_row(png_ptr);

               return;

            }

            break;

         case 1:

            if ((png_ptr->row_number & 0x07) != 0 || 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) != 0 || 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) != 0 || png_ptr->width < 2)

            {

               png_write_finish_row(png_ptr);

               return;

            }

            break;

         case 6:

            if ((png_ptr->row_number & 0x01) == 0)

            {

               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) != 0)

   {

      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 == 0)

      {

         png_write_finish_row(png_ptr);

         return;

      }

   }

#endif

#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED

   /* Handle other transformations */

   if (png_ptr->transformations != 0)

      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) != 0 &&

       (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 */