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
ff_png_zalloc(void * opaque,unsigned int items,unsigned int size)39 void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
40 {
41 return av_mallocz_array(items, size);
42 }
43
ff_png_zfree(void * opaque,void * ptr)44 void ff_png_zfree(void *opaque, void *ptr)
45 {
46 av_free(ptr);
47 }
48
ff_png_get_nb_channels(int color_type)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 */
ff_png_pass_row_size(int pass,int bits_per_pixel,int width)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