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/* pngwtran.c - transforms the data in a row for png writers
libpng 1.0 beta 3 - version 0.89
For conditions of distribution and use, see copyright notice in png.h
Copyright (c) 1995, 1996 Guy Eric Schalnat, Group 42, Inc.
May 25, 1996
*/
#define PNG_INTERNAL
#include "png.h"
/* transform the data according to the users wishes. The order of
transformations is significant. */
void
png_do_write_transformations(png_structp png_ptr)
{
#if defined(PNG_WRITE_FILLER_SUPPORTED)
if (png_ptr->transformations & PNG_FILLER)
png_do_write_filler(&(png_ptr->row_info), png_ptr->row_buf + 1,
png_ptr->flags);
#endif
#if defined(PNG_WRITE_PACK_SUPPORTED)
if (png_ptr->transformations & PNG_PACK)
png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
png_ptr->bit_depth);
#endif
#if defined(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
#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
#if defined(PNG_WRITE_BGR_SUPPORTED)
if (png_ptr->transformations & PNG_BGR)
png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
#if defined(PNG_WRITE_INVERT_SUPPORTED)
if (png_ptr->transformations & PNG_INVERT_MONO)
png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
#endif
}
#if defined(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
png_do_pack(png_row_infop row_info, png_bytep row, png_byte bit_depth)
{
if (row_info && row && row_info->bit_depth == 8 &&
row_info->channels == 1)
{
switch (bit_depth)
{
case 1:
{
png_bytep sp;
png_bytep dp;
int mask;
png_int_32 i;
int v;
sp = row;
dp = row;
mask = 0x80;
v = 0;
for (i = 0; i < row_info->width; i++)
{
if (*sp)
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;
png_bytep dp;
int shift;
png_int_32 i;
int v;
png_byte value;
sp = row;
dp = row;
shift = 6;
v = 0;
for (i = 0; i < row_info->width; i++)
{
value = (png_byte)(*sp & 0x3);
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;
png_bytep dp;
int shift;
png_int_32 i;
int v;
png_byte value;
sp = row;
dp = row;
shift = 4;
v = 0;
for (i = 0; i < row_info->width; i++)
{
value = (png_byte)(*sp & 0xf);
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;
}
}
row_info->bit_depth = bit_depth;
row_info->pixel_depth = (png_uint_16)(bit_depth * row_info->channels);
row_info->rowbytes =
((row_info->width * row_info->pixel_depth + 7) >> 3);
}
}
#endif
#if defined(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
png_do_shift(png_row_infop row_info, png_bytep row, png_color_8p bit_depth)
{
if (row && row_info &&
row_info->color_type != PNG_COLOR_TYPE_PALETTE)
{
int shift_start[4], shift_dec[4];
int channels;
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 dephts, could only be grayscale, so one channel */
if (row_info->bit_depth < 8)
{
png_bytep bp;
png_uint_32 i;
int j;
png_byte mask;
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 (bp = row, i = 0; i < row_info->rowbytes; i++, bp++)
{
int v;
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;
png_uint_32 i;
int j;
for (bp = row, i = 0; i < row_info->width; i++)
{
int c;
for (c = 0; c < channels; c++, bp++)
{
int v;
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;
int j;
for (bp = row, i = 0;
i < row_info->width * row_info->channels;
i++)
{
int c;
for (c = 0; c < channels; c++, bp += 2)
{
png_uint_16 value, v;
v = (png_uint_16)(((png_uint_16)(*bp) << 8) +
(png_uint_16)(*(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 + 1) = (png_byte)(value & 0xff);
}
}
}
}
}
#endif
#ifdef PNG_WRITE_FILLER_SUPPORTED
/* remove filler byte */
void
png_do_write_filler(png_row_infop row_info, png_bytep row,
png_byte flags)
{
if (row && row_info && row_info->color_type == PNG_COLOR_TYPE_RGB &&
row_info->bit_depth == 8)
{
if (flags & PNG_FLAG_FILLER_AFTER)
{
png_bytep sp, dp;
png_uint_32 i;
for (i = 1, sp = row + 4, dp = row + 3;
i < row_info->width;
i++)
{
*dp++ = *sp++;
*dp++ = *sp++;
*dp++ = *sp++;
sp++;
}
row_info->channels = 3;
row_info->pixel_depth = 24;
row_info->rowbytes = row_info->width * 3;
}
else
{
png_bytep sp, dp;
png_uint_32 i;
for (i = 0, sp = row, dp = row;
i < row_info->width;
i++)
{
sp++;
*dp++ = *sp++;
*dp++ = *sp++;
*dp++ = *sp++;
}
row_info->channels = 3;
row_info->pixel_depth = 24;
row_info->rowbytes = row_info->width * 3;
}
}
}
#endif
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