Libav
png.c
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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 */
30  0x80, 0x80, 0x08, 0x88, 0x22, 0xaa, 0x55,
31 };
32 
33 /* minimum x value */
35  0, 4, 0, 2, 0, 1, 0
36 };
37 
38 /* x shift to get row width */
40  3, 3, 2, 2, 1, 1, 0
41 };
42 
43 /* Mask to determine which pixels are valid in a pass */
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  return av_mallocz_array(items, size);
51 }
52 
53 void ff_png_zfree(void *opaque, void *ptr)
54 {
55  av_free(ptr);
56 }
57 
58 int ff_png_get_nb_channels(int color_type)
59 {
60  int channels;
61  channels = 1;
62  if ((color_type & (PNG_COLOR_MASK_COLOR | PNG_COLOR_MASK_PALETTE)) ==
64  channels = 3;
65  if (color_type & PNG_COLOR_MASK_ALPHA)
66  channels++;
67  return channels;
68 }
69 
70 /* compute the row size of an interleaved pass */
71 int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
72 {
73  int shift, xmin, pass_width;
74 
75  xmin = ff_png_pass_xmin[pass];
76  if (width <= xmin)
77  return 0;
78  shift = ff_png_pass_xshift[pass];
79  pass_width = (width - xmin + (1 << shift) - 1) >> shift;
80  return (pass_width * bits_per_pixel + 7) >> 3;
81 }
static const uint8_t ff_png_pass_xmin[NB_PASSES]
Definition: png.c:34
int size
uint8_t
void av_free(void *ptr)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc(). ...
Definition: mem.c:186
#define PNG_COLOR_MASK_PALETTE
Definition: png.h:27
int ff_png_get_nb_channels(int color_type)
Definition: png.c:58
Libavcodec external API header.
#define NB_PASSES
Definition: png.h:50
#define PNG_COLOR_MASK_COLOR
Definition: png.h:28
#define pass
Definition: fft_template.c:335
const uint8_t ff_mngsig[8]
Definition: png.c:26
static int width
Definition: utils.c:156
const uint8_t ff_png_pass_mask[NB_PASSES]
Definition: png.c:44
const uint8_t ff_png_pass_ymask[NB_PASSES]
Definition: png.c:29
#define PNG_COLOR_MASK_ALPHA
Definition: png.h:29
static const uint8_t ff_png_pass_xshift[NB_PASSES]
Definition: png.c:39
const uint8_t ff_pngsig[8]
Definition: png.c:25
void ff_png_zfree(void *opaque, void *ptr)
Definition: png.c:53
int ff_png_pass_row_size(int pass, int bits_per_pixel, int width)
Definition: png.c:71
static void * av_mallocz_array(size_t nmemb, size_t size)
Definition: mem.h:205
void * ff_png_zalloc(void *opaque, unsigned int items, unsigned int size)
Definition: png.c:48