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4349 | Serge | 1 | /* |
2 | * PNG image format |
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3 | * Copyright (c) 2003 Fabrice Bellard |
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4 | * |
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5 | * This file is part of FFmpeg. |
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6 | * |
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7 | * FFmpeg is free software; you can redistribute it and/or |
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8 | * modify it under the terms of the GNU Lesser General Public |
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9 | * License as published by the Free Software Foundation; either |
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10 | * version 2.1 of the License, or (at your option) any later version. |
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11 | * |
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12 | * FFmpeg is distributed in the hope that it will be useful, |
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13 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
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14 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU |
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15 | * Lesser General Public License for more details. |
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16 | * |
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17 | * You should have received a copy of the GNU Lesser General Public |
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18 | * License along with FFmpeg; if not, write to the Free Software |
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19 | * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA |
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20 | */ |
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21 | #include "avcodec.h" |
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22 | #include "png.h" |
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23 | |||
24 | /* Mask to determine which y pixels are valid in a pass */ |
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25 | const uint8_t ff_png_pass_ymask[NB_PASSES] = { |
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26 | 0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, |
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27 | }; |
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28 | |||
29 | /* minimum x value */ |
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30 | static const uint8_t ff_png_pass_xmin[NB_PASSES] = { |
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31 | 0, 4, 0, 2, 0, 1, 0 |
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32 | }; |
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33 | |||
34 | /* x shift to get row width */ |
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35 | static const uint8_t ff_png_pass_xshift[NB_PASSES] = { |
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36 | 3, 3, 2, 2, 1, 1, 0 |
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37 | }; |
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38 | |||
39 | void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size) |
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40 | { |
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41 | return av_mallocz_array(items, size); |
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42 | } |
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43 | |||
44 | void ff_png_zfree(void *opaque, void *ptr) |
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45 | { |
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46 | av_free(ptr); |
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47 | } |
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48 | |||
49 | int ff_png_get_nb_channels(int color_type) |
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50 | { |
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51 | int channels; |
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52 | channels = 1; |
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53 | if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) == |
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54 | PNG_COLOR_MASK_COLOR) |
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55 | channels = 3; |
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56 | if (color_type & PNG_COLOR_MASK_ALPHA) |
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57 | channels++; |
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58 | return channels; |
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59 | } |
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60 | |||
61 | /* compute the row size of an interleaved pass */ |
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62 | int ff_png_pass_row_size(int pass, int bits_per_pixel, int width) |
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63 | { |
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64 | int shift, xmin, pass_width; |
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65 | |||
66 | xmin = ff_png_pass_xmin[pass]; |
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67 | if (width <= xmin) |
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68 | return 0; |
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69 | shift = ff_png_pass_xshift[pass]; |
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70 | pass_width = (width - xmin + (1 << shift) - 1) >> shift; |
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71 | return (pass_width * bits_per_pixel + 7) >> 3; |
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72 | }><>=> |