blob: ef52b51bd43eebb7323846024dfa3223dd9d0e69
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 | } |
73 |