Statistics
| Branch: | Revision:

ffmpeg / libavcodec / png.c @ 2912e87a

History | View | Annotate | Download (2.39 KB)

1
/*
2
 * PNG image format
3
 * Copyright (c) 2003 Fabrice Bellard
4
 *
5
 * This file is part of Libav.
6
 *
7
 * Libav 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
 * Libav 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 Libav; 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 "bytestream.h"
23
#include "png.h"
24

    
25
const uint8_t ff_pngsig[8] = {137, 80, 78, 71, 13, 10, 26, 10};
26
const uint8_t ff_mngsig[8] = {138, 77, 78, 71, 13, 10, 26, 10};
27

    
28
/* Mask to determine which y pixels are valid in a pass */
29
const uint8_t ff_png_pass_ymask[NB_PASSES] = {
30
    0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
31
};
32

    
33
/* minimum x value */
34
static const uint8_t ff_png_pass_xmin[NB_PASSES] = {
35
    0, 4, 0, 2, 0, 1, 0
36
};
37

    
38
/* x shift to get row width */
39
static const uint8_t ff_png_pass_xshift[NB_PASSES] = {
40
    3, 3, 2, 2, 1, 1, 0
41
};
42

    
43
/* Mask to determine which pixels are valid in a pass */
44
const uint8_t ff_png_pass_mask[NB_PASSES] = {
45
    0x80, 0x08, 0x88, 0x22, 0xaa, 0x55, 0xff
46
};
47

    
48
void *ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
49
{
50
    if(items >= UINT_MAX / size)
51
        return NULL;
52
    return av_malloc(items * size);
53
}
54

    
55
void ff_png_zfree(void *opaque, void *ptr)
56
{
57
    av_free(ptr);
58
}
59

    
60
int ff_png_get_nb_channels(int color_type)
61
{
62
    int channels;
63
    channels = 1;
64
    if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
65
        PNG_COLOR_MASK_COLOR)
66
        channels = 3;
67
    if (color_type & PNG_COLOR_MASK_ALPHA)
68
        channels++;
69
    return channels;
70
}
71

    
72
/* compute the row size of an interleaved pass */
73
int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
74
{
75
    int shift, xmin, pass_width;
76

    
77
    xmin = ff_png_pass_xmin[pass];
78
    if (width <= xmin)
79
        return 0;
80
    shift = ff_png_pass_xshift[pass];
81
    pass_width = (width - xmin + (1 << shift) - 1) >> shift;
82
    return (pass_width * bits_per_pixel + 7) >> 3;
83
}