This repository has been archived on 2023-11-11. You can view files and clone it, but cannot push or open issues or pull requests.
libpng/pngwtran.c

564 lines
17 KiB
C
Raw Normal View History

1995-07-20 07:43:20 +00:00
1997-05-16 07:46:07 +00:00
/* pngwtran.c - transforms the data in a row for PNG writers
1998-01-01 13:13:13 +00:00
*
2001-03-30 12:42:28 +00:00
* libpng 1.0.10 - March 30, 2001
1998-01-01 13:13:13 +00:00
* For conditions of distribution and use, see copyright notice in png.h
2001-01-22 14:52:16 +00:00
* Copyright (c) 1998-2001 Glenn Randers-Pehrson
2000-06-04 19:29:29 +00:00
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
1998-01-01 13:13:13 +00:00
*/
1995-07-20 07:43:20 +00:00
#define PNG_INTERNAL
#include "png.h"
2001-03-14 13:08:39 +00:00
#ifdef PNG_WRITE_SUPPORTED
1995-07-20 07:43:20 +00:00
1998-06-14 19:43:31 +00:00
/* Transform the data according to the user's wishes. The order of
1998-01-01 13:13:13 +00:00
* transformations is significant.
*/
2000-05-06 19:09:57 +00:00
void /* PRIVATE */
1995-12-19 09:22:19 +00:00
png_do_write_transformations(png_structp png_ptr)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_debug(1, "in png_do_write_transformations\n");
1998-03-07 12:06:55 +00:00
1999-12-10 15:43:02 +00:00
if (png_ptr == NULL)
return;
1998-03-07 12:06:55 +00:00
#if defined(PNG_WRITE_USER_TRANSFORM_SUPPORTED)
if (png_ptr->transformations & PNG_USER_TRANSFORM)
if(png_ptr->write_user_transform_fn != NULL)
(*(png_ptr->write_user_transform_fn)) /* user write transform function */
(png_ptr, /* png_ptr */
&(png_ptr->row_info), /* row_info: */
/* png_uint_32 width; width of row */
/* png_uint_32 rowbytes; number of bytes in row */
/* png_byte color_type; color type of pixels */
/* png_byte bit_depth; bit depth of samples */
/* png_byte channels; number of channels (1-4) */
/* png_byte pixel_depth; bits per pixel (depth*channels) */
png_ptr->row_buf + 1); /* start of pixel data for row */
#endif
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_FILLER_SUPPORTED)
1995-12-19 09:22:19 +00:00
if (png_ptr->transformations & PNG_FILLER)
1997-05-16 07:46:07 +00:00
png_do_strip_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
1996-06-05 20:50:50 +00:00
png_ptr->flags);
1995-09-26 10:22:39 +00:00
#endif
1998-01-31 03:45:12 +00:00
#if defined(PNG_WRITE_PACKSWAP_SUPPORTED)
if (png_ptr->transformations & PNG_PACKSWAP)
png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_PACK_SUPPORTED)
1995-07-20 07:43:20 +00:00
if (png_ptr->transformations & PNG_PACK)
png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
1997-05-16 07:46:07 +00:00
(png_uint_32)png_ptr->bit_depth);
1995-09-26 10:22:39 +00:00
#endif
1998-12-29 17:47:59 +00:00
#if defined(PNG_WRITE_SWAP_SUPPORTED)
if (png_ptr->transformations & PNG_SWAP_BYTES)
png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_SHIFT_SUPPORTED)
1995-07-20 07:43:20 +00:00
if (png_ptr->transformations & PNG_SHIFT)
png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
&(png_ptr->shift));
1995-09-26 10:22:39 +00:00
#endif
1998-01-17 04:06:18 +00:00
#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
if (png_ptr->transformations & PNG_INVERT_ALPHA)
png_do_write_invert_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
1998-02-28 13:00:24 +00:00
#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
if (png_ptr->transformations & PNG_SWAP_ALPHA)
png_do_write_swap_alpha(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_BGR_SUPPORTED)
1995-07-20 07:43:20 +00:00
if (png_ptr->transformations & PNG_BGR)
png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
1995-09-26 10:22:39 +00:00
#endif
#if defined(PNG_WRITE_INVERT_SUPPORTED)
1995-07-20 07:43:20 +00:00
if (png_ptr->transformations & PNG_INVERT_MONO)
png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
1995-09-26 10:22:39 +00:00
#endif
1995-07-20 07:43:20 +00:00
}
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_PACK_SUPPORTED)
1998-01-01 13:13:13 +00:00
/* Pack pixels into bytes. Pass the true bit depth in bit_depth. The
* row_info bit depth should be 8 (one pixel per byte). The channels
* should be 1 (this only happens on grayscale and paletted images).
*/
2000-05-06 19:09:57 +00:00
void /* PRIVATE */
1997-05-16 07:46:07 +00:00
png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_debug(1, "in png_do_pack\n");
if (row_info->bit_depth == 8 &&
#if defined(PNG_USELESS_TESTS_SUPPORTED)
row != NULL && row_info != NULL &&
#endif
1995-07-20 07:43:20 +00:00
row_info->channels == 1)
{
1997-05-16 07:46:07 +00:00
switch ((int)bit_depth)
1995-07-20 07:43:20 +00:00
{
case 1:
{
1997-05-16 07:46:07 +00:00
png_bytep sp, dp;
int mask, v;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1995-07-20 07:43:20 +00:00
sp = row;
dp = row;
mask = 0x80;
v = 0;
1998-12-29 17:47:59 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0; i < row_width; i++)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
if (*sp != 0)
1995-07-20 07:43:20 +00:00
v |= mask;
sp++;
if (mask > 1)
mask >>= 1;
else
{
mask = 0x80;
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
dp++;
1995-07-20 07:43:20 +00:00
v = 0;
}
}
if (mask != 0x80)
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
1995-07-20 07:43:20 +00:00
break;
}
case 2:
{
1997-05-16 07:46:07 +00:00
png_bytep sp, dp;
int shift, v;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1995-07-20 07:43:20 +00:00
sp = row;
dp = row;
shift = 6;
v = 0;
1998-05-02 17:52:25 +00:00
for (i = 0; i < row_width; i++)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_byte value;
2000-02-05 05:40:16 +00:00
value = (png_byte)(*sp & 0x03);
1995-07-20 07:43:20 +00:00
v |= (value << shift);
if (shift == 0)
{
shift = 6;
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
1995-07-20 07:43:20 +00:00
dp++;
v = 0;
}
else
shift -= 2;
sp++;
}
if (shift != 6)
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
1995-07-20 07:43:20 +00:00
break;
}
case 4:
{
1997-05-16 07:46:07 +00:00
png_bytep sp, dp;
int shift, v;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1995-07-20 07:43:20 +00:00
sp = row;
dp = row;
shift = 4;
v = 0;
1998-05-02 17:52:25 +00:00
for (i = 0; i < row_width; i++)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_byte value;
2000-02-05 05:40:16 +00:00
value = (png_byte)(*sp & 0x0f);
1995-07-20 07:43:20 +00:00
v |= (value << shift);
if (shift == 0)
{
shift = 4;
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
1995-07-20 07:43:20 +00:00
dp++;
v = 0;
}
else
shift -= 4;
sp++;
}
if (shift != 4)
1996-01-26 07:38:47 +00:00
*dp = (png_byte)v;
1995-07-20 07:43:20 +00:00
break;
}
}
1997-05-16 07:46:07 +00:00
row_info->bit_depth = (png_byte)bit_depth;
row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
1995-07-20 07:43:20 +00:00
row_info->rowbytes =
((row_info->width * row_info->pixel_depth + 7) >> 3);
}
}
1995-09-26 10:22:39 +00:00
#endif
1995-07-20 07:43:20 +00:00
1995-09-26 10:22:39 +00:00
#if defined(PNG_WRITE_SHIFT_SUPPORTED)
1998-01-01 13:13:13 +00:00
/* Shift pixel values to take advantage of whole range. Pass the
* true number of bits in bit_depth. The row should be packed
* according to row_info->bit_depth. Thus, if you had a row of
* bit depth 4, but the pixels only had values from 0 to 7, you
* would pass 3 as bit_depth, and this routine would translate the
* data to 0 to 15.
*/
2000-05-06 19:09:57 +00:00
void /* PRIVATE */
1995-12-19 09:22:19 +00:00
png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_debug(1, "in png_do_shift\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
if (row != NULL && row_info != NULL &&
#else
if (
#endif
1995-07-20 07:43:20 +00:00
row_info->color_type != PNG_COLOR_TYPE_PALETTE)
{
int shift_start[4], shift_dec[4];
1998-05-09 15:02:29 +00:00
int channels = 0;
1995-07-20 07:43:20 +00:00
if (row_info->color_type & PNG_COLOR_MASK_COLOR)
{
shift_start[channels] = row_info->bit_depth - bit_depth->red;
shift_dec[channels] = bit_depth->red;
channels++;
shift_start[channels] = row_info->bit_depth - bit_depth->green;
shift_dec[channels] = bit_depth->green;
channels++;
shift_start[channels] = row_info->bit_depth - bit_depth->blue;
shift_dec[channels] = bit_depth->blue;
channels++;
}
else
{
shift_start[channels] = row_info->bit_depth - bit_depth->gray;
shift_dec[channels] = bit_depth->gray;
channels++;
}
if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
{
shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
shift_dec[channels] = bit_depth->alpha;
channels++;
}
1998-02-28 13:00:24 +00:00
/* with low row depths, could only be grayscale, so one channel */
1995-07-20 07:43:20 +00:00
if (row_info->bit_depth < 8)
{
1998-05-02 17:52:25 +00:00
png_bytep bp = row;
png_uint_32 i;
1995-07-20 07:43:20 +00:00
png_byte mask;
1998-05-02 17:52:25 +00:00
png_uint_32 row_bytes = row_info->rowbytes;
1995-07-20 07:43:20 +00:00
if (bit_depth->gray == 1 && row_info->bit_depth == 2)
mask = 0x55;
else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
mask = 0x11;
else
mask = 0xff;
1998-05-02 17:52:25 +00:00
for (i = 0; i < row_bytes; i++, bp++)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_uint_16 v;
int j;
1995-07-20 07:43:20 +00:00
v = *bp;
*bp = 0;
for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
{
if (j > 0)
*bp |= (png_byte)((v << j) & 0xff);
else
*bp |= (png_byte)((v >> (-j)) & mask);
}
}
}
else if (row_info->bit_depth == 8)
{
1998-05-02 17:52:25 +00:00
png_bytep bp = row;
png_uint_32 i;
1998-05-09 15:02:29 +00:00
png_uint_32 istop = channels * row_info->width;
1995-07-20 07:43:20 +00:00
1998-05-09 15:02:29 +00:00
for (i = 0; i < istop; i++, bp++)
1995-07-20 07:43:20 +00:00
{
1998-05-09 15:02:29 +00:00
png_uint_16 v;
int j;
int c = (int)(i%channels);
1995-07-20 07:43:20 +00:00
1998-05-09 15:02:29 +00:00
v = *bp;
*bp = 0;
for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
{
if (j > 0)
*bp |= (png_byte)((v << j) & 0xff);
else
*bp |= (png_byte)((v >> (-j)) & 0xff);
1995-07-20 07:43:20 +00:00
}
}
}
else
{
1995-12-19 09:22:19 +00:00
png_bytep bp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
1998-05-09 15:02:29 +00:00
png_uint_32 istop = channels * row_info->width;
1995-07-20 07:43:20 +00:00
1998-05-09 15:02:29 +00:00
for (bp = row, i = 0; i < istop; i++)
1995-07-20 07:43:20 +00:00
{
1998-05-09 15:02:29 +00:00
int c = (int)(i%channels);
png_uint_16 value, v;
int j;
1995-07-20 07:43:20 +00:00
1999-10-14 12:43:10 +00:00
v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
1998-05-09 15:02:29 +00:00
value = 0;
for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
1995-07-20 07:43:20 +00:00
{
1998-05-09 15:02:29 +00:00
if (j > 0)
value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
else
value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
1995-07-20 07:43:20 +00:00
}
1998-05-09 15:02:29 +00:00
*bp++ = (png_byte)(value >> 8);
*bp++ = (png_byte)(value & 0xff);
1995-07-20 07:43:20 +00:00
}
}
}
}
1995-09-26 10:22:39 +00:00
#endif
1995-07-20 07:43:20 +00:00
1997-05-16 07:46:07 +00:00
#if defined(PNG_WRITE_SWAP_ALPHA_SUPPORTED)
2000-05-06 19:09:57 +00:00
void /* PRIVATE */
1997-05-16 07:46:07 +00:00
png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
png_debug(1, "in png_do_write_swap_alpha\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
if (row != NULL && row_info != NULL)
#endif
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
/* This converts from ARGB to RGBA */
if (row_info->bit_depth == 8)
{
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
1997-05-16 07:46:07 +00:00
{
1998-04-21 20:03:57 +00:00
png_byte save = *(sp++);
1997-05-16 07:46:07 +00:00
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save;
}
}
/* This converts from AARRGGBB to RRGGBBAA */
else
1995-09-26 10:22:39 +00:00
{
1997-05-16 07:46:07 +00:00
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1997-05-16 07:46:07 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1997-05-16 07:46:07 +00:00
{
1998-04-21 20:03:57 +00:00
png_byte save[2];
1997-05-16 07:46:07 +00:00
save[0] = *(sp++);
save[1] = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save[0];
*(dp++) = save[1];
}
1995-09-26 10:22:39 +00:00
}
}
1997-05-16 07:46:07 +00:00
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
1995-07-20 07:43:20 +00:00
{
1997-05-16 07:46:07 +00:00
/* This converts from AG to GA */
if (row_info->bit_depth == 8)
{
png_bytep sp, dp;
png_uint_32 i;
1998-05-02 17:52:25 +00:00
png_uint_32 row_width = row_info->width;
1995-09-26 10:22:39 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1997-05-16 07:46:07 +00:00
{
1998-04-21 20:03:57 +00:00
png_byte save = *(sp++);
1997-05-16 07:46:07 +00:00
*(dp++) = *(sp++);
*(dp++) = save;
}
}
/* This converts from AAGG to GGAA */
else
1995-09-26 10:22:39 +00:00
{
1997-05-16 07:46:07 +00:00
png_bytep sp, dp;
png_uint_32 i;
1998-05-02 17:52:25 +00:00
png_uint_32 row_width = row_info->width;
1997-05-16 07:46:07 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1997-05-16 07:46:07 +00:00
{
1998-04-21 20:03:57 +00:00
png_byte save[2];
1997-05-16 07:46:07 +00:00
save[0] = *(sp++);
save[1] = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save[0];
*(dp++) = save[1];
}
1995-09-26 10:22:39 +00:00
}
1995-07-20 07:43:20 +00:00
}
}
}
1995-09-26 10:22:39 +00:00
#endif
1995-07-20 07:43:20 +00:00
1998-01-17 04:06:18 +00:00
#if defined(PNG_WRITE_INVERT_ALPHA_SUPPORTED)
2000-05-06 19:09:57 +00:00
void /* PRIVATE */
1998-01-17 04:06:18 +00:00
png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_write_invert_alpha\n");
#if defined(PNG_USELESS_TESTS_SUPPORTED)
if (row != NULL && row_info != NULL)
#endif
{
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
/* This inverts the alpha channel in RGBA */
if (row_info->bit_depth == 8)
{
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
1998-01-17 04:06:18 +00:00
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
1999-10-14 12:43:10 +00:00
*(dp++) = (png_byte)(255 - *(sp++));
1998-01-17 04:06:18 +00:00
}
}
/* This inverts the alpha channel in RRGGBBAA */
else
{
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1998-01-17 04:06:18 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1998-01-17 04:06:18 +00:00
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
1999-10-14 12:43:10 +00:00
*(dp++) = (png_byte)(255 - *(sp++));
*(dp++) = (png_byte)(255 - *(sp++));
1998-01-17 04:06:18 +00:00
}
}
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
/* This inverts the alpha channel in GA */
if (row_info->bit_depth == 8)
{
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1998-01-17 04:06:18 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1998-01-17 04:06:18 +00:00
{
*(dp++) = *(sp++);
1999-10-14 12:43:10 +00:00
*(dp++) = (png_byte)(255 - *(sp++));
1998-01-17 04:06:18 +00:00
}
}
/* This inverts the alpha channel in GGAA */
else
{
png_bytep sp, dp;
1998-05-02 17:52:25 +00:00
png_uint_32 i;
png_uint_32 row_width = row_info->width;
1998-01-17 04:06:18 +00:00
1998-05-02 17:52:25 +00:00
for (i = 0, sp = dp = row; i < row_width; i++)
1998-01-17 04:06:18 +00:00
{
*(dp++) = *(sp++);
*(dp++) = *(sp++);
1999-10-14 12:43:10 +00:00
*(dp++) = (png_byte)(255 - *(sp++));
*(dp++) = (png_byte)(255 - *(sp++));
1998-01-17 04:06:18 +00:00
}
}
}
}
}
#endif
2000-12-15 14:54:42 +00:00
#if defined(PNG_MNG_FEATURES_SUPPORTED)
/* undoes intrapixel differencing */
void /* PRIVATE */
png_do_write_intrapixel(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_write_intrapixel\n");
if (
#if defined(PNG_USELESS_TESTS_SUPPORTED)
row != NULL && row_info != NULL &&
#endif
(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);
}
}
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=(s0-s1)&0xffff;
png_uint_32 blue=(s2-s1)&0xffff;
*(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_MNG_FEATURES_SUPPORTED */
2001-03-14 13:08:39 +00:00
#endif /* PNG_WRITE_SUPPORTED */