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84 lines
2.4 KiB
C
84 lines
2.4 KiB
C
/*
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* PNG image format
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* Copyright (c) 2003 Fabrice Bellard
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*
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* This file is part of FFmpeg.
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*
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* FFmpeg is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* FFmpeg is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with FFmpeg; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include "avcodec.h"
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#include "bytestream.h"
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#include "png.h"
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const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
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const uint8_t ff_mngsig[8] = {138, 77, 78, 71, 13, 10, 26, 10};
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/* Mask to determine which y pixels are valid in a pass */
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const uint8_t ff_png_pass_ymask[NB_PASSES] = {
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0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
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};
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/* minimum x value */
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const uint8_t ff_png_pass_xmin[NB_PASSES] = {
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0, 4, 0, 2, 0, 1, 0
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};
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/* x shift to get row width */
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const uint8_t ff_png_pass_xshift[NB_PASSES] = {
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3, 3, 2, 2, 1, 1, 0
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};
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/* Mask to determine which pixels are valid in a pass */
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const uint8_t ff_png_pass_mask[NB_PASSES] = {
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0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff
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};
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void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
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{
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if(items >= UINT_MAX / size)
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return NULL;
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return av_malloc(items * size);
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}
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void ff_png_zfree(void *opaque, void *ptr)
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{
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av_free(ptr);
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}
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int ff_png_get_nb_channels(int color_type)
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{
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int channels;
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channels = 1;
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if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
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PNG_COLOR_MASK_COLOR)
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channels = 3;
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if (color_type & PNG_COLOR_MASK_ALPHA)
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channels++;
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return channels;
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}
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/* compute the row size of an interleaved pass */
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int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
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{
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int shift, xmin, pass_width;
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xmin = ff_png_pass_xmin[pass];
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if (width <= xmin)
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return 0;
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shift = ff_png_pass_xshift[pass];
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pass_width = (width - xmin + (1 << shift) - 1) >> shift;
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return (pass_width * bits_per_pixel + 7) >> 3;
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}
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