mirror of
https://git.code.sf.net/p/libpng/code.git
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Imported from libpng-0.71.tar
This commit is contained in:
Guy Schalnat
331
pngwtran.c
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331
pngwtran.c
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/* pngwtran.c - transforms the data in a row for png writers
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libpng 1.0 beta 1 - version 0.71
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For conditions of distribution and use, see copyright notice in png.h
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Copyright (c) 1995 Guy Eric Schalnat, Group 42, Inc.
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June 26, 1995
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*/
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#define PNG_INTERNAL
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#include "png.h"
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/* transform the data according to the users wishes. The order of
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transformations is significant. */
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void
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png_do_write_transformations(png_struct *png_ptr)
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{
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if (png_ptr->transformations & PNG_RGBA)
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png_do_write_rgbx(&(png_ptr->row_info), png_ptr->row_buf + 1);
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if (png_ptr->transformations & PNG_XRGB)
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png_do_write_xrgb(&(png_ptr->row_info), png_ptr->row_buf + 1);
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if (png_ptr->transformations & PNG_PACK)
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png_do_pack(&(png_ptr->row_info), png_ptr->row_buf + 1,
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png_ptr->bit_depth);
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if (png_ptr->transformations & PNG_SHIFT)
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png_do_shift(&(png_ptr->row_info), png_ptr->row_buf + 1,
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&(png_ptr->shift));
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if (png_ptr->transformations & PNG_SWAP_BYTES)
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png_do_swap(&(png_ptr->row_info), png_ptr->row_buf + 1);
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if (png_ptr->transformations & PNG_BGR)
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png_do_bgr(&(png_ptr->row_info), png_ptr->row_buf + 1);
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if (png_ptr->transformations & PNG_INVERT_MONO)
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png_do_invert(&(png_ptr->row_info), png_ptr->row_buf + 1);
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}
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/* pack pixels into bytes. Pass the true bit depth in bit_depth. The
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row_info bit depth should be 8 (one pixel per byte). The channels
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should be 1 (this only happens on grayscale and paletted images) */
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void
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png_do_pack(png_row_info *row_info, png_byte *row, png_byte bit_depth)
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{
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if (row_info && row && row_info->bit_depth == 8 &&
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row_info->channels == 1)
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{
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switch (bit_depth)
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{
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case 1:
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{
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png_byte *sp;
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png_byte *dp;
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int mask;
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png_int_32 i;
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int v;
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sp = row;
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dp = row;
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mask = 0x80;
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v = 0;
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for (i = 0; i < row_info->width; i++)
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{
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if (*sp)
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v |= mask;
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sp++;
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if (mask > 1)
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mask >>= 1;
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else
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{
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mask = 0x80;
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*dp = v;
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dp++;
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v = 0;
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}
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}
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if (mask != 0x80)
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*dp = v;
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break;
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}
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case 2:
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{
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png_byte *sp;
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png_byte *dp;
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int shift;
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png_int_32 i;
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int v;
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png_byte value;
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sp = row;
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dp = row;
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shift = 6;
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v = 0;
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for (i = 0; i < row_info->width; i++)
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{
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value = *sp & 0x3;
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v |= (value << shift);
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if (shift == 0)
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{
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shift = 6;
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*dp = v;
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dp++;
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v = 0;
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}
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else
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shift -= 2;
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sp++;
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}
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if (shift != 6)
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*dp = v;
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break;
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}
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case 4:
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{
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png_byte *sp;
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png_byte *dp;
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int shift;
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png_int_32 i;
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int v;
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png_byte value;
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sp = row;
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dp = row;
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shift = 4;
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v = 0;
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for (i = 0; i < row_info->width; i++)
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{
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value = *sp & 0xf;
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v |= (value << shift);
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if (shift == 0)
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{
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shift = 4;
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*dp = v;
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dp++;
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v = 0;
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}
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else
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shift -= 4;
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sp++;
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}
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if (shift != 4)
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*dp = v;
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break;
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}
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}
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row_info->bit_depth = bit_depth;
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row_info->pixel_depth = bit_depth * row_info->channels;
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row_info->rowbytes =
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((row_info->width * row_info->pixel_depth + 7) >> 3);
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}
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}
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/* shift pixel values to take advantage of whole range. Pass the
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true number of bits in bit_depth. The row should be packed
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according to row_info->bit_depth. Thus, if you had a row of
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bit depth 4, but the pixels only had values from 0 to 7, you
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would pass 3 as bit_depth, and this routine would translate the
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data to 0 to 15. */
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void
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png_do_shift(png_row_info *row_info, png_byte *row, png_color_8 *bit_depth)
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{
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if (row && row_info &&
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row_info->color_type != PNG_COLOR_TYPE_PALETTE)
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{
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int shift_start[4], shift_dec[4];
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int channels;
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channels = 0;
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if (row_info->color_type & PNG_COLOR_MASK_COLOR)
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{
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shift_start[channels] = row_info->bit_depth - bit_depth->red;
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shift_dec[channels] = bit_depth->red;
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channels++;
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shift_start[channels] = row_info->bit_depth - bit_depth->green;
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shift_dec[channels] = bit_depth->green;
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channels++;
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shift_start[channels] = row_info->bit_depth - bit_depth->blue;
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shift_dec[channels] = bit_depth->blue;
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channels++;
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}
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else
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{
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shift_start[channels] = row_info->bit_depth - bit_depth->gray;
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shift_dec[channels] = bit_depth->gray;
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channels++;
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}
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if (row_info->color_type & PNG_COLOR_MASK_ALPHA)
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{
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shift_start[channels] = row_info->bit_depth - bit_depth->alpha;
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shift_dec[channels] = bit_depth->alpha;
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channels++;
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}
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/* with low row dephts, could only be grayscale, so one channel */
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if (row_info->bit_depth < 8)
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{
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png_byte *bp;
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png_uint_32 i;
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int j;
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png_byte mask;
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if (bit_depth->gray == 1 && row_info->bit_depth == 2)
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mask = 0x55;
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else if (row_info->bit_depth == 4 && bit_depth->gray == 3)
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mask = 0x11;
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else
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mask = 0xff;
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for (bp = row, i = 0; i < row_info->rowbytes; i++, bp++)
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{
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int v;
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v = *bp;
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*bp = 0;
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for (j = shift_start[0]; j > -shift_dec[0]; j -= shift_dec[0])
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{
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if (j > 0)
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*bp |= (png_byte)((v << j) & 0xff);
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else
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*bp |= (png_byte)((v >> (-j)) & mask);
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}
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}
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}
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else if (row_info->bit_depth == 8)
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{
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png_byte *bp;
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png_uint_32 i;
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int j;
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for (bp = row, i = 0; i < row_info->width; i++)
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{
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int c;
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for (c = 0; c < channels; c++, bp++)
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{
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int v;
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v = *bp;
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*bp = 0;
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for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
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{
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if (j > 0)
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*bp |= (png_byte)((v << j) & 0xff);
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else
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*bp |= (png_byte)((v >> (-j)) & 0xff);
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}
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}
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}
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}
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else
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{
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png_byte *bp;
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png_uint_32 i;
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int j;
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for (bp = row, i = 0;
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i < row_info->width * row_info->channels;
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i++)
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{
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int c;
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for (c = 0; c < channels; c++, bp += 2)
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{
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png_uint_16 value, v;
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v = ((png_uint_16)(*bp) << 8) + (png_uint_16)(*(bp + 1));
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value = 0;
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for (j = shift_start[c]; j > -shift_dec[c]; j -= shift_dec[c])
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{
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if (j > 0)
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value |= (png_uint_16)((v << j) & (png_uint_16)0xffff);
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else
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value |= (png_uint_16)((v >> (-j)) & (png_uint_16)0xffff);
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}
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*bp = value >> 8;
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*(bp + 1) = value & 0xff;
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}
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}
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}
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}
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}
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/* remove filler byte after rgb */
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void
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png_do_write_rgbx(png_row_info *row_info, png_byte *row)
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{
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if (row && row_info && row_info->color_type == PNG_COLOR_TYPE_RGB &&
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row_info->bit_depth == 8)
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{
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png_byte *sp, *dp;
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png_uint_32 i;
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for (i = 1, sp = row + 4, dp = row + 3;
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i < row_info->width;
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i++)
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{
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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sp++;
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}
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row_info->channels = 3;
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row_info->pixel_depth = 24;
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row_info->rowbytes = row_info->width * 3;
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}
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}
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/* remove filler byte before rgb */
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void
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png_do_write_xrgb(png_row_info *row_info, png_byte *row)
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{
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if (row && row_info && row_info->color_type == PNG_COLOR_TYPE_RGB &&
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row_info->bit_depth == 8)
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{
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png_byte *sp, *dp;
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png_uint_32 i;
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for (i = 0, sp = row, dp = row;
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i < row_info->width;
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i++)
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{
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sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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*dp++ = *sp++;
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}
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row_info->channels = 3;
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row_info->pixel_depth = 24;
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row_info->rowbytes = row_info->width * 3;
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}
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}
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