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 */
25const uint8_t ff_png_pass_ymask[NB_PASSES] = {
26    0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
27};
28
29/* minimum x value */
30static 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 */
35static const uint8_t ff_png_pass_xshift[NB_PASSES] = {
36    3, 3, 2, 2, 1, 1, 0
37};
38
39void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
40{
41    return av_mallocz_array(items, size);
42}
43
44void ff_png_zfree(void *opaque, void *ptr)
45{
46    av_free(ptr);
47}
48
49int 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 */
62int 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