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64 lines
1.9 KiB
64 lines
1.9 KiB
/* |
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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 <stdint.h> |
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#include "libavutil/mem.h" |
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#include "png.h" |
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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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static 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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static 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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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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