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png.c
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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 */
26  0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
27 };
28 
29 /* minimum x value */
31  0, 4, 0, 2, 0, 1, 0
32 };
33 
34 /* x shift to get row width */
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)) ==
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 }
static int shift(int a, int b)
Definition: sonic.c:82
static const uint8_t ff_png_pass_xmin[NB_PASSES]
Definition: png.c:30
uint8_t
ptrdiff_t size
Definition: opengl_enc.c:101
#define PNG_COLOR_MASK_PALETTE
Definition: png.h:27
int ff_png_get_nb_channels(int color_type)
Definition: png.c:49
#define NB_PASSES
Definition: png.h:50
#define PNG_COLOR_MASK_COLOR
Definition: png.h:28
#define pass
Definition: fft_template.c:532
Libavcodec external API header.
const uint8_t ff_png_pass_ymask[NB_PASSES]
Definition: png.c:25
#define PNG_COLOR_MASK_ALPHA
Definition: png.h:29
static const uint8_t ff_png_pass_xshift[NB_PASSES]
Definition: png.c:35
void ff_png_zfree(void *opaque, void *ptr)
Definition: png.c:44
#define av_free(p)
int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
Definition: png.c:62
static void * av_mallocz_array(size_t nmemb, size_t size)
Definition: mem.h:229
void * ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
Definition: png.c:39
static int width