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pngwtran.c
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/* pngwtran.c - transforms the data in a row for PNG writers
*
* Last changed in libpng 1.5.4 [July 7, 2011]
* Copyright (c) 1998-2011 Glenn Randers-Pehrson
* (Version 0.96 Copyright (c) 1996, 1997 Andreas Dilger)
* (Version 0.88 Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.)
*
* This code is released under the libpng license.
* For conditions of distribution and use, see the disclaimer
* and license in png.h
*/
#include "pngpriv.h"
#ifdef PNG_WRITE_SUPPORTED
#ifdef PNG_WRITE_TRANSFORMS_SUPPORTED
/* Transform the data according to the user's wishes. The order of
* transformations is significant.
*/
void /* PRIVATE */
png_do_write_transformations(png_structp png_ptr)
{
png_debug(1, "in png_do_write_transformations");
if (png_ptr == NULL)
return;
#ifdef 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_size_t 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
#ifdef PNG_WRITE_FILLER_SUPPORTED
if (png_ptr->transformations & PNG_FILLER)
png_do_strip_channel(&(png_ptr->row_info), png_ptr->row_buf + 1,
!(png_ptr->flags & PNG_FLAG_FILLER_AFTER));
#endif
#ifdef PNG_WRITE_PACKSWAP_SUPPORTED
if (png_ptr->transformations & PNG_PACKSWAP)
png_do_packswap(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#ifdef PNG_WRITE_PACK_SUPPORTED
if (png_ptr->transformations & PNG_PACK)
png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
(png_uint_32)png_ptr->bit_depth);
#endif
#ifdef PNG_WRITE_SWAP_SUPPORTED
if (png_ptr->transformations & PNG_SWAP_BYTES)
png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#ifdef PNG_WRITE_SHIFT_SUPPORTED
if (png_ptr->transformations & PNG_SHIFT)
png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
&(png_ptr->shift));
#endif
#ifdef 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
#ifdef 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
#ifdef PNG_WRITE_BGR_SUPPORTED
if (png_ptr->transformations & PNG_BGR)
png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#ifdef PNG_WRITE_INVERT_SUPPORTED
if (png_ptr->transformations & PNG_INVERT_MONO)
png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
}
#ifdef PNG_WRITE_PACK_SUPPORTED
/* 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).
*/
void /* PRIVATE */
png_do_pack(png_row_infop row_info, png_bytep row, png_uint_32 bit_depth)
{
png_debug(1, "in png_do_pack");
if (row_info->bit_depth == 8 &&
row_info->channels == 1)
{
switch ((int)bit_depth)
{
case 1:
{
png_bytep sp, dp;
int mask, v;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
sp = row;
dp = row;
mask = 0x80;
v = 0;
for (i = 0; i < row_width; i++)
{
if (*sp != 0)
v |= mask;
sp++;
if (mask > 1)
mask >>= 1;
else
{
mask = 0x80;
*dp = (png_byte)v;
dp++;
v = 0;
}
}
if (mask != 0x80)
*dp = (png_byte)v;
break;
}
case 2:
{
png_bytep sp, dp;
int shift, v;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
sp = row;
dp = row;
shift = 6;
v = 0;
for (i = 0; i < row_width; i++)
{
png_byte value;
value = (png_byte)(*sp & 0x03);
v |= (value << shift);
if (shift == 0)
{
shift = 6;
*dp = (png_byte)v;
dp++;
v = 0;
}
else
shift -= 2;
sp++;
}
if (shift != 6)
*dp = (png_byte)v;
break;
}
case 4:
{
png_bytep sp, dp;
int shift, v;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
sp = row;
dp = row;
shift = 4;
v = 0;
for (i = 0; i < row_width; i++)
{
png_byte value;
value = (png_byte)(*sp & 0x0f);
v |= (value << shift);
if (shift == 0)
{
shift = 4;
*dp = (png_byte)v;
dp++;
v = 0;
}
else
shift -= 4;
sp++;
}
if (shift != 4)
*dp = (png_byte)v;
break;
}
default:
break;
}
row_info->bit_depth = (png_byte)bit_depth;
row_info->pixel_depth = (png_byte)(bit_depth * row_info->channels);
row_info->rowbytes = PNG_ROWBYTES(row_info->pixel_depth,
row_info->width);
}
}
#endif
#ifdef PNG_WRITE_SHIFT_SUPPORTED
/* 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.
*/
void /* PRIVATE */
png_do_shift(png_row_infop row_info, png_bytep row,
png_const_color_8p bit_depth)
{
png_debug(1, "in png_do_shift");
if (row_info->color_type != PNG_COLOR_TYPE_PALETTE)
{
int shift_start[4], shift_dec[4];
int channels = 0;
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++;
}
/* With low row depths, could only be grayscale, so one channel */
if (row_info->bit_depth < 8)
{
png_bytep bp = row;
png_size_t i;
png_byte mask;
png_size_t row_bytes = row_info->rowbytes;
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;
for (i = 0; i < row_bytes; i++, bp++)
{
png_uint_16 v;
int j;
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)
{
png_bytep bp = row;
png_uint_32 i;
png_uint_32 istop = channels * row_info->width;
for (i = 0; i < istop; i++, bp++)
{
png_uint_16 v;
int j;
int c = (int)(i%channels);
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);
}
}
}
else
{
png_bytep bp;
png_uint_32 i;
png_uint_32 istop = channels * row_info->width;
for (bp = row, i = 0; i < istop; i++)
{
int c = (int)(i%channels);
png_uint_16 value, v;
int j;
v = (png_uint_16)(((png_uint_16)(*bp) << 8) + *(bp + 1));
value = 0;
for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
{
if (j > 0)
value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
else
value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
}
*bp++ = (png_byte)(value >> 8);
*bp++ = (png_byte)(value & 0xff);
}
}
}
}
#endif
#ifdef PNG_WRITE_SWAP_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_write_swap_alpha(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_write_swap_alpha");
{
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This converts from ARGB to RGBA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
png_byte save = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save;
}
}
#ifdef PNG_WRITE_16BIT_SUPPORTED
else
{
/* This converts from AARRGGBB to RRGGBBAA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
png_byte save[2];
save[0] = *(sp++);
save[1] = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save[0];
*(dp++) = save[1];
}
}
#endif /* PNG_WRITE_16BIT_SUPPORTED */
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This converts from AG to GA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
png_byte save = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save;
}
}
#ifdef PNG_WRITE_16BIT_SUPPORTED
else
{
/* This converts from AAGG to GGAA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
png_byte save[2];
save[0] = *(sp++);
save[1] = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = save[0];
*(dp++) = save[1];
}
}
#endif /* PNG_WRITE_16BIT_SUPPORTED */
}
}
}
#endif
#ifdef PNG_WRITE_INVERT_ALPHA_SUPPORTED
void /* PRIVATE */
png_do_write_invert_alpha(png_row_infop row_info, png_bytep row)
{
png_debug(1, "in png_do_write_invert_alpha");
{
if (row_info->color_type == PNG_COLOR_TYPE_RGB_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This inverts the alpha channel in RGBA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
/* Does nothing
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*/
sp+=3; dp = sp;
*(dp++) = (png_byte)(255 - *(sp++));
}
}
#ifdef PNG_WRITE_16BIT_SUPPORTED
else
{
/* This inverts the alpha channel in RRGGBBAA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
/* Does nothing
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*/
sp+=6; dp = sp;
*(dp++) = (png_byte)(255 - *(sp++));
*(dp++) = (png_byte)(255 - *(sp++));
}
}
#endif /* PNG_WRITE_16BIT_SUPPORTED */
}
else if (row_info->color_type == PNG_COLOR_TYPE_GRAY_ALPHA)
{
if (row_info->bit_depth == 8)
{
/* This inverts the alpha channel in GA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
*(dp++) = *(sp++);
*(dp++) = (png_byte)(255 - *(sp++));
}
}
#ifdef PNG_WRITE_16BIT_SUPPORTED
else
{
/* This inverts the alpha channel in GGAA */
png_bytep sp, dp;
png_uint_32 i;
png_uint_32 row_width = row_info->width;
for (i = 0, sp = dp = row; i < row_width; i++)
{
/* Does nothing
*(dp++) = *(sp++);
*(dp++) = *(sp++);
*/
sp+=2; dp = sp;
*(dp++) = (png_byte)(255 - *(sp++));
*(dp++) = (png_byte)(255 - *(sp++));
}
}
#endif /* PNG_WRITE_16BIT_SUPPORTED */
}
}
}
#endif
#endif /* PNG_WRITE_TRANSFORMS_SUPPORTED */
#ifdef 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");
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 */
#endif /* PNG_WRITE_SUPPORTED */

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