1.1 --- /dev/null	Thu Jan 01 00:00:00 1970 +0000
     1.2 +++ b/libs/libpng/pngwtran.c	Thu Sep 08 06:28:38 2011 +0300
     1.3 @@ -0,0 +1,572 @@
     1.4 +
     1.5 +/* pngwtran.c - transforms the data in a row for PNG writers
     1.6 + *
     1.7 + * Last changed in libpng 1.2.9 April 14, 2006
     1.8 + * For conditions of distribution and use, see copyright notice in png.h
     1.9 + * Copyright (c) 1998-2006 Glenn Randers-Pehrson
    1.10 + * (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
    1.11 + * (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
    1.12 + */
    1.13 +
    1.14 +#define PNG_INTERNAL
    1.15 +#include "png.h"
    1.16 +#ifdef PNG_WRITE_SUPPORTED
    1.17 +
    1.18 +/* Transform the data according to the user's wishes.  The order of
    1.19 + * transformations is significant.
    1.20 + */
    1.21 +void /* PRIVATE */
    1.22 +png_do_write_transformations(png_structp png_ptr)
    1.23 +{
    1.24 +   png_debug(1, "in png_do_write_transformations\n");
    1.25 +
    1.26 +   if (png_ptr == NULL)
    1.27 +      return;
    1.28 +
    1.29 +#if defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
    1.30 +   if (png_ptr->transformations & PNG_USER_TRANSFORM)
    1.31 +      if (png_ptr->write_user_transform_fn != NULL)
    1.32 +        (*(png_ptr->write_user_transform_fn)) /* user write transform function */
    1.33 +          (png_ptr,                    /* png_ptr */
    1.34 +           &(png_ptr->row_info),       /* row_info:     */
    1.35 +             /*  png_uint_32 width;          width of row */
    1.36 +             /*  png_uint_32 rowbytes;       number of bytes in row */
    1.37 +             /*  png_byte color_type;        color type of pixels */
    1.38 +             /*  png_byte bit_depth;         bit depth of samples */
    1.39 +             /*  png_byte channels;          number of channels (1-4) */
    1.40 +             /*  png_byte pixel_depth;       bits per pixel (depth*channels) */
    1.41 +           png_ptr->row_buf + 1);      /* start of pixel data for row */
    1.42 +#endif
    1.43 +#if defined(PNG_WRITE_FILLER_SUPPORTED)
    1.44 +   if (png_ptr->transformations & PNG_FILLER)
    1.45 +      png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
    1.46 +         png_ptr->flags);
    1.47 +#endif
    1.48 +#if defined(PNG_WRITE_PACKSWAP_SUPPORTED)
    1.49 +   if (png_ptr->transformations & PNG_PACKSWAP)
    1.50 +      png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.51 +#endif
    1.52 +#if defined(PNG_WRITE_PACK_SUPPORTED)
    1.53 +   if (png_ptr->transformations & PNG_PACK)
    1.54 +      png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
    1.55 +         (png_uint_32)png_ptr->bit_depth);
    1.56 +#endif
    1.57 +#if defined(PNG_WRITE_SWAP_SUPPORTED)
    1.58 +   if (png_ptr->transformations & PNG_SWAP_BYTES)
    1.59 +      png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.60 +#endif
    1.61 +#if defined(PNG_WRITE_SHIFT_SUPPORTED)
    1.62 +   if (png_ptr->transformations & PNG_SHIFT)
    1.63 +      png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
    1.64 +         &(png_ptr->shift));
    1.65 +#endif
    1.66 +#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
    1.67 +   if (png_ptr->transformations & PNG_SWAP_ALPHA)
    1.68 +      png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.69 +#endif
    1.70 +#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
    1.71 +   if (png_ptr->transformations & PNG_INVERT_ALPHA)
    1.72 +      png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.73 +#endif
    1.74 +#if defined(PNG_WRITE_BGR_SUPPORTED)
    1.75 +   if (png_ptr->transformations & PNG_BGR)
    1.76 +      png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.77 +#endif
    1.78 +#if defined(PNG_WRITE_INVERT_SUPPORTED)
    1.79 +   if (png_ptr->transformations & PNG_INVERT_MONO)
    1.80 +      png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
    1.81 +#endif
    1.82 +}
    1.83 +
    1.84 +#if defined(PNG_WRITE_PACK_SUPPORTED)
    1.85 +/* Pack pixels into bytes.  Pass the true bit depth in bit_depth.  The
    1.86 + * row_info bit depth should be 8 (one pixel per byte).  The channels
    1.87 + * should be 1 (this only happens on grayscale and paletted images).
    1.88 + */
    1.89 +void /* PRIVATE */
    1.90 +png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
    1.91 +{
    1.92 +   png_debug(1, "in png_do_pack\n");
    1.93 +   if (row_info->bit_depth == 8 &&
    1.94 +#if defined(PNG_USELESS_TESTS_SUPPORTED)
    1.95 +       row != NULL && row_info != NULL &&
    1.96 +#endif
    1.97 +      row_info->channels == 1)
    1.98 +   {
    1.99 +      switch ((int)bit_depth)
   1.100 +      {
   1.101 +         case 1:
   1.102 +         {
   1.103 +            png_bytep sp, dp;
   1.104 +            int mask, v;
   1.105 +            png_uint_32 i;
   1.106 +            png_uint_32 row_width = row_info->width;
   1.107 +
   1.108 +            sp = row;
   1.109 +            dp = row;
   1.110 +            mask = 0x80;
   1.111 +            v = 0;
   1.112 +
   1.113 +            for (i = 0; i < row_width; i++)
   1.114 +            {
   1.115 +               if (*sp != 0)
   1.116 +                  v |= mask;
   1.117 +               sp++;
   1.118 +               if (mask > 1)
   1.119 +                  mask >>= 1;
   1.120 +               else
   1.121 +               {
   1.122 +                  mask = 0x80;
   1.123 +                  *dp = (png_byte)v;
   1.124 +                  dp++;
   1.125 +                  v = 0;
   1.126 +               }
   1.127 +            }
   1.128 +            if (mask != 0x80)
   1.129 +               *dp = (png_byte)v;
   1.130 +            break;
   1.131 +         }
   1.132 +         case 2:
   1.133 +         {
   1.134 +            png_bytep sp, dp;
   1.135 +            int shift, v;
   1.136 +            png_uint_32 i;
   1.137 +            png_uint_32 row_width = row_info->width;
   1.138 +
   1.139 +            sp = row;
   1.140 +            dp = row;
   1.141 +            shift = 6;
   1.142 +            v = 0;
   1.143 +            for (i = 0; i < row_width; i++)
   1.144 +            {
   1.145 +               png_byte value;
   1.146 +
   1.147 +               value = (png_byte)(*sp & 0x03);
   1.148 +               v |= (value << shift);
   1.149 +               if (shift == 0)
   1.150 +               {
   1.151 +                  shift = 6;
   1.152 +                  *dp = (png_byte)v;
   1.153 +                  dp++;
   1.154 +                  v = 0;
   1.155 +               }
   1.156 +               else
   1.157 +                  shift -= 2;
   1.158 +               sp++;
   1.159 +            }
   1.160 +            if (shift != 6)
   1.161 +               *dp = (png_byte)v;
   1.162 +            break;
   1.163 +         }
   1.164 +         case 4:
   1.165 +         {
   1.166 +            png_bytep sp, dp;
   1.167 +            int shift, v;
   1.168 +            png_uint_32 i;
   1.169 +            png_uint_32 row_width = row_info->width;
   1.170 +
   1.171 +            sp = row;
   1.172 +            dp = row;
   1.173 +            shift = 4;
   1.174 +            v = 0;
   1.175 +            for (i = 0; i < row_width; i++)
   1.176 +            {
   1.177 +               png_byte value;
   1.178 +
   1.179 +               value = (png_byte)(*sp & 0x0f);
   1.180 +               v |= (value << shift);
   1.181 +
   1.182 +               if (shift == 0)
   1.183 +               {
   1.184 +                  shift = 4;
   1.185 +                  *dp = (png_byte)v;
   1.186 +                  dp++;
   1.187 +                  v = 0;
   1.188 +               }
   1.189 +               else
   1.190 +                  shift -= 4;
   1.191 +
   1.192 +               sp++;
   1.193 +            }
   1.194 +            if (shift != 4)
   1.195 +               *dp = (png_byte)v;
   1.196 +            break;
   1.197 +         }
   1.198 +      }
   1.199 +      row_info->bit_depth = (png_byte)bit_depth;
   1.200 +      row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
   1.201 +      row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
   1.202 +         row_info->width);
   1.203 +   }
   1.204 +}
   1.205 +#endif
   1.206 +
   1.207 +#if defined(PNG_WRITE_SHIFT_SUPPORTED)
   1.208 +/* Shift pixel values to take advantage of whole range.  Pass the
   1.209 + * true number of bits in bit_depth.  The row should be packed
   1.210 + * according to row_info->bit_depth.  Thus, if you had a row of
   1.211 + * bit depth 4, but the pixels only had values from 0 to 7, you
   1.212 + * would pass 3 as bit_depth, and this routine would translate the
   1.213 + * data to 0 to 15.
   1.214 + */
   1.215 +void /* PRIVATE */
   1.216 +png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
   1.217 +{
   1.218 +   png_debug(1, "in png_do_shift\n");
   1.219 +#if defined(PNG_USELESS_TESTS_SUPPORTED)
   1.220 +   if (row != NULL && row_info != NULL &&
   1.221 +#else
   1.222 +   if (
   1.223 +#endif
   1.224 +      row_info->color_type != PNG_COLOR_TYPE_PALETTE)
   1.225 +   {
   1.226 +      int shift_start[4], shift_dec[4];
   1.227 +      int channels = 0;
   1.228 +
   1.229 +      if (row_info->color_type & PNG_COLOR_MASK_COLOR)
   1.230 +      {
   1.231 +         shift_start[channels] = row_info->bit_depth - bit_depth->red;
   1.232 +         shift_dec[channels] = bit_depth->red;
   1.233 +         channels++;
   1.234 +         shift_start[channels] = row_info->bit_depth - bit_depth->green;
   1.235 +         shift_dec[channels] = bit_depth->green;
   1.236 +         channels++;
   1.237 +         shift_start[channels] = row_info->bit_depth - bit_depth->blue;
   1.238 +         shift_dec[channels] = bit_depth->blue;
   1.239 +         channels++;
   1.240 +      }
   1.241 +      else
   1.242 +      {
   1.243 +         shift_start[channels] = row_info->bit_depth - bit_depth->gray;
   1.244 +         shift_dec[channels] = bit_depth->gray;
   1.245 +         channels++;
   1.246 +      }
   1.247 +      if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
   1.248 +      {
   1.249 +         shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
   1.250 +         shift_dec[channels] = bit_depth->alpha;
   1.251 +         channels++;
   1.252 +      }
   1.253 +
   1.254 +      /* with low row depths, could only be grayscale, so one channel */
   1.255 +      if (row_info->bit_depth < 8)
   1.256 +      {
   1.257 +         png_bytep bp = row;
   1.258 +         png_uint_32 i;
   1.259 +         png_byte mask;
   1.260 +         png_uint_32 row_bytes = row_info->rowbytes;
   1.261 +
   1.262 +         if (bit_depth->gray == 1 && row_info->bit_depth == 2)
   1.263 +            mask = 0x55;
   1.264 +         else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
   1.265 +            mask = 0x11;
   1.266 +         else
   1.267 +            mask = 0xff;
   1.268 +
   1.269 +         for (i = 0; i < row_bytes; i++, bp++)
   1.270 +         {
   1.271 +            png_uint_16 v;
   1.272 +            int j;
   1.273 +
   1.274 +            v = *bp;
   1.275 +            *bp = 0;
   1.276 +            for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
   1.277 +            {
   1.278 +               if (j > 0)
   1.279 +                  *bp |= (png_byte)((v << j) & 0xff);
   1.280 +               else
   1.281 +                  *bp |= (png_byte)((v >> (-j)) & mask);
   1.282 +            }
   1.283 +         }
   1.284 +      }
   1.285 +      else if (row_info->bit_depth == 8)
   1.286 +      {
   1.287 +         png_bytep bp = row;
   1.288 +         png_uint_32 i;
   1.289 +         png_uint_32 istop = channels * row_info->width;
   1.290 +
   1.291 +         for (i = 0; i < istop; i++, bp++)
   1.292 +         {
   1.293 +
   1.294 +            png_uint_16 v;
   1.295 +            int j;
   1.296 +            int c = (int)(i%channels);
   1.297 +
   1.298 +            v = *bp;
   1.299 +            *bp = 0;
   1.300 +            for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
   1.301 +            {
   1.302 +               if (j > 0)
   1.303 +                  *bp |= (png_byte)((v << j) & 0xff);
   1.304 +               else
   1.305 +                  *bp |= (png_byte)((v >> (-j)) & 0xff);
   1.306 +            }
   1.307 +         }
   1.308 +      }
   1.309 +      else
   1.310 +      {
   1.311 +         png_bytep bp;
   1.312 +         png_uint_32 i;
   1.313 +         png_uint_32 istop = channels * row_info->width;
   1.314 +
   1.315 +         for (bp = row, i = 0; i < istop; i++)
   1.316 +         {
   1.317 +            int c = (int)(i%channels);
   1.318 +            png_uint_16 value, v;
   1.319 +            int j;
   1.320 +
   1.321 +            v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
   1.322 +            value = 0;
   1.323 +            for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
   1.324 +            {
   1.325 +               if (j > 0)
   1.326 +                  value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
   1.327 +               else
   1.328 +                  value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
   1.329 +            }
   1.330 +            *bp++ = (png_byte)(value >> 8);
   1.331 +            *bp++ = (png_byte)(value & 0xff);
   1.332 +         }
   1.333 +      }
   1.334 +   }
   1.335 +}
   1.336 +#endif
   1.337 +
   1.338 +#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
   1.339 +void /* PRIVATE */
   1.340 +png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
   1.341 +{
   1.342 +   png_debug(1, "in png_do_write_swap_alpha\n");
   1.343 +#if defined(PNG_USELESS_TESTS_SUPPORTED)
   1.344 +   if (row != NULL && row_info != NULL)
   1.345 +#endif
   1.346 +   {
   1.347 +      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
   1.348 +      {
   1.349 +         /* This converts from ARGB to RGBA */
   1.350 +         if (row_info->bit_depth == 8)
   1.351 +         {
   1.352 +            png_bytep sp, dp;
   1.353 +            png_uint_32 i;
   1.354 +            png_uint_32 row_width = row_info->width;
   1.355 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.356 +            {
   1.357 +               png_byte save = *(sp++);
   1.358 +               *(dp++) = *(sp++);
   1.359 +               *(dp++) = *(sp++);
   1.360 +               *(dp++) = *(sp++);
   1.361 +               *(dp++) = save;
   1.362 +            }
   1.363 +         }
   1.364 +         /* This converts from AARRGGBB to RRGGBBAA */
   1.365 +         else
   1.366 +         {
   1.367 +            png_bytep sp, dp;
   1.368 +            png_uint_32 i;
   1.369 +            png_uint_32 row_width = row_info->width;
   1.370 +
   1.371 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.372 +            {
   1.373 +               png_byte save[2];
   1.374 +               save[0] = *(sp++);
   1.375 +               save[1] = *(sp++);
   1.376 +               *(dp++) = *(sp++);
   1.377 +               *(dp++) = *(sp++);
   1.378 +               *(dp++) = *(sp++);
   1.379 +               *(dp++) = *(sp++);
   1.380 +               *(dp++) = *(sp++);
   1.381 +               *(dp++) = *(sp++);
   1.382 +               *(dp++) = save[0];
   1.383 +               *(dp++) = save[1];
   1.384 +            }
   1.385 +         }
   1.386 +      }
   1.387 +      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
   1.388 +      {
   1.389 +         /* This converts from AG to GA */
   1.390 +         if (row_info->bit_depth == 8)
   1.391 +         {
   1.392 +            png_bytep sp, dp;
   1.393 +            png_uint_32 i;
   1.394 +            png_uint_32 row_width = row_info->width;
   1.395 +
   1.396 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.397 +            {
   1.398 +               png_byte save = *(sp++);
   1.399 +               *(dp++) = *(sp++);
   1.400 +               *(dp++) = save;
   1.401 +            }
   1.402 +         }
   1.403 +         /* This converts from AAGG to GGAA */
   1.404 +         else
   1.405 +         {
   1.406 +            png_bytep sp, dp;
   1.407 +            png_uint_32 i;
   1.408 +            png_uint_32 row_width = row_info->width;
   1.409 +
   1.410 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.411 +            {
   1.412 +               png_byte save[2];
   1.413 +               save[0] = *(sp++);
   1.414 +               save[1] = *(sp++);
   1.415 +               *(dp++) = *(sp++);
   1.416 +               *(dp++) = *(sp++);
   1.417 +               *(dp++) = save[0];
   1.418 +               *(dp++) = save[1];
   1.419 +            }
   1.420 +         }
   1.421 +      }
   1.422 +   }
   1.423 +}
   1.424 +#endif
   1.425 +
   1.426 +#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
   1.427 +void /* PRIVATE */
   1.428 +png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
   1.429 +{
   1.430 +   png_debug(1, "in png_do_write_invert_alpha\n");
   1.431 +#if defined(PNG_USELESS_TESTS_SUPPORTED)
   1.432 +   if (row != NULL && row_info != NULL)
   1.433 +#endif
   1.434 +   {
   1.435 +      if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
   1.436 +      {
   1.437 +         /* This inverts the alpha channel in RGBA */
   1.438 +         if (row_info->bit_depth == 8)
   1.439 +         {
   1.440 +            png_bytep sp, dp;
   1.441 +            png_uint_32 i;
   1.442 +            png_uint_32 row_width = row_info->width;
   1.443 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.444 +            {
   1.445 +               /* does nothing
   1.446 +               *(dp++) = *(sp++);
   1.447 +               *(dp++) = *(sp++);
   1.448 +               *(dp++) = *(sp++);
   1.449 +               */
   1.450 +               sp+=3; dp = sp;
   1.451 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.452 +            }
   1.453 +         }
   1.454 +         /* This inverts the alpha channel in RRGGBBAA */
   1.455 +         else
   1.456 +         {
   1.457 +            png_bytep sp, dp;
   1.458 +            png_uint_32 i;
   1.459 +            png_uint_32 row_width = row_info->width;
   1.460 +
   1.461 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.462 +            {
   1.463 +               /* does nothing
   1.464 +               *(dp++) = *(sp++);
   1.465 +               *(dp++) = *(sp++);
   1.466 +               *(dp++) = *(sp++);
   1.467 +               *(dp++) = *(sp++);
   1.468 +               *(dp++) = *(sp++);
   1.469 +               *(dp++) = *(sp++);
   1.470 +               */
   1.471 +               sp+=6; dp = sp;
   1.472 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.473 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.474 +            }
   1.475 +         }
   1.476 +      }
   1.477 +      else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
   1.478 +      {
   1.479 +         /* This inverts the alpha channel in GA */
   1.480 +         if (row_info->bit_depth == 8)
   1.481 +         {
   1.482 +            png_bytep sp, dp;
   1.483 +            png_uint_32 i;
   1.484 +            png_uint_32 row_width = row_info->width;
   1.485 +
   1.486 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.487 +            {
   1.488 +               *(dp++) = *(sp++);
   1.489 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.490 +            }
   1.491 +         }
   1.492 +         /* This inverts the alpha channel in GGAA */
   1.493 +         else
   1.494 +         {
   1.495 +            png_bytep sp, dp;
   1.496 +            png_uint_32 i;
   1.497 +            png_uint_32 row_width = row_info->width;
   1.498 +
   1.499 +            for (i = 0, sp = dp = row; i < row_width; i++)
   1.500 +            {
   1.501 +               /* does nothing
   1.502 +               *(dp++) = *(sp++);
   1.503 +               *(dp++) = *(sp++);
   1.504 +               */
   1.505 +               sp+=2; dp = sp;
   1.506 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.507 +               *(dp++) = (png_byte)(255 - *(sp++));
   1.508 +            }
   1.509 +         }
   1.510 +      }
   1.511 +   }
   1.512 +}
   1.513 +#endif
   1.514 +
   1.515 +#if defined(PNG_MNG_FEATURES_SUPPORTED)
   1.516 +/* undoes intrapixel differencing  */
   1.517 +void /* PRIVATE */
   1.518 +png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
   1.519 +{
   1.520 +   png_debug(1, "in png_do_write_intrapixel\n");
   1.521 +   if (
   1.522 +#if defined(PNG_USELESS_TESTS_SUPPORTED)
   1.523 +       row != NULL && row_info != NULL &&
   1.524 +#endif
   1.525 +       (row_info->color_type & PNG_COLOR_MASK_COLOR))
   1.526 +   {
   1.527 +      int bytes_per_pixel;
   1.528 +      png_uint_32 row_width = row_info->width;
   1.529 +      if (row_info->bit_depth == 8)
   1.530 +      {
   1.531 +         png_bytep rp;
   1.532 +         png_uint_32 i;
   1.533 +
   1.534 +         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
   1.535 +            bytes_per_pixel = 3;
   1.536 +         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
   1.537 +            bytes_per_pixel = 4;
   1.538 +         else
   1.539 +            return;
   1.540 +
   1.541 +         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
   1.542 +         {
   1.543 +            *(rp)   = (png_byte)((*rp     - *(rp+1))&0xff);
   1.544 +            *(rp+2) = (png_byte)((*(rp+2) - *(rp+1))&0xff);
   1.545 +         }
   1.546 +      }
   1.547 +      else if (row_info->bit_depth == 16)
   1.548 +      {
   1.549 +         png_bytep rp;
   1.550 +         png_uint_32 i;
   1.551 +
   1.552 +         if (row_info->color_type == PNG_COLOR_TYPE_RGB)
   1.553 +            bytes_per_pixel = 6;
   1.554 +         else if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
   1.555 +            bytes_per_pixel = 8;
   1.556 +         else
   1.557 +            return;
   1.558 +
   1.559 +         for (i = 0, rp = row; i < row_width; i++, rp += bytes_per_pixel)
   1.560 +         {
   1.561 +            png_uint_32 s0   = (*(rp  ) << 8) | *(rp+1);
   1.562 +            png_uint_32 s1   = (*(rp+2) << 8) | *(rp+3);
   1.563 +            png_uint_32 s2   = (*(rp+4) << 8) | *(rp+5);
   1.564 +            png_uint_32 red  = (png_uint_32)((s0 - s1) & 0xffffL);
   1.565 +            png_uint_32 blue = (png_uint_32)((s2 - s1) & 0xffffL);
   1.566 +            *(rp  ) = (png_byte)((red >> 8) & 0xff);
   1.567 +            *(rp+1) = (png_byte)(red & 0xff);
   1.568 +            *(rp+4) = (png_byte)((blue >> 8) & 0xff);
   1.569 +            *(rp+5) = (png_byte)(blue & 0xff);
   1.570 +         }
   1.571 +      }
   1.572 +   }
   1.573 +}
   1.574 +#endif /* PNG_MNG_FEATURES_SUPPORTED */
   1.575 +#endif /* PNG_WRITE_SUPPORTED */