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