gif.c
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1 /*
2  * GIF encoder.
3  * Copyright (c) 2000 Fabrice Bellard
4  * Copyright (c) 2002 Francois Revol
5  * Copyright (c) 2006 Baptiste Coudurier
6  *
7  * This file is part of Libav.
8  *
9  * Libav is free software; you can redistribute it and/or
10  * modify it under the terms of the GNU Lesser General Public
11  * License as published by the Free Software Foundation; either
12  * version 2.1 of the License, or (at your option) any later version.
13  *
14  * Libav is distributed in the hope that it will be useful,
15  * but WITHOUT ANY WARRANTY; without even the implied warranty of
16  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17  * Lesser General Public License for more details.
18  *
19  * You should have received a copy of the GNU Lesser General Public
20  * License along with Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 /*
25  * First version by Francois Revol revol@free.fr
26  *
27  * Features and limitations:
28  * - currently no compression is performed,
29  * in fact the size of the data is 9/8 the size of the image in 8bpp
30  * - uses only a global standard palette
31  * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
32  *
33  * Reference documents:
34  * http://www.goice.co.jp/member/mo/formats/gif.html
35  * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
36  * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
37  *
38  * this url claims to have an LZW algorithm not covered by Unisys patent:
39  * http://www.msg.net/utility/whirlgif/gifencod.html
40  * could help reduce the size of the files _a lot_...
41  * some sites mentions an RLE type compression also.
42  */
43 
44 #include "avcodec.h"
45 #include "bytestream.h"
46 #include "lzw.h"
47 
48 /* The GIF format uses reversed order for bitstreams... */
49 /* at least they don't use PDP_ENDIAN :) */
50 #define BITSTREAM_WRITER_LE
51 
52 #include "put_bits.h"
53 
54 typedef struct {
57  uint8_t *buf;
58 } GIFContext;
59 
60 /* GIF header */
62  uint8_t **bytestream, uint32_t *palette)
63 {
64  int i;
65  unsigned int v;
66 
67  bytestream_put_buffer(bytestream, "GIF", 3);
68  bytestream_put_buffer(bytestream, "89a", 3);
69  bytestream_put_le16(bytestream, avctx->width);
70  bytestream_put_le16(bytestream, avctx->height);
71 
72  bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
73  bytestream_put_byte(bytestream, 0x1f); /* background color index */
74  bytestream_put_byte(bytestream, 0); /* aspect ratio */
75 
76  /* the global palette */
77  for(i=0;i<256;i++) {
78  v = palette[i];
79  bytestream_put_be24(bytestream, v);
80  }
81 
82  return 0;
83 }
84 
86  uint8_t **bytestream, uint8_t *end,
87  const uint8_t *buf, int linesize)
88 {
89  GIFContext *s = avctx->priv_data;
90  int len = 0, height;
91  const uint8_t *ptr;
92  /* image block */
93 
94  bytestream_put_byte(bytestream, 0x2c);
95  bytestream_put_le16(bytestream, 0);
96  bytestream_put_le16(bytestream, 0);
97  bytestream_put_le16(bytestream, avctx->width);
98  bytestream_put_le16(bytestream, avctx->height);
99  bytestream_put_byte(bytestream, 0x00); /* flags */
100  /* no local clut */
101 
102  bytestream_put_byte(bytestream, 0x08);
103 
104  ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,
105  12, FF_LZW_GIF, put_bits);
106 
107  ptr = buf;
108  for (height = avctx->height; height--;) {
109  len += ff_lzw_encode(s->lzw, ptr, avctx->width);
110  ptr += linesize;
111  }
113 
114  ptr = s->buf;
115  while (len > 0) {
116  int size = FFMIN(255, len);
117  bytestream_put_byte(bytestream, size);
118  if (end - *bytestream < size)
119  return -1;
120  bytestream_put_buffer(bytestream, ptr, size);
121  ptr += size;
122  len -= size;
123  }
124  bytestream_put_byte(bytestream, 0x00); /* end of image block */
125  bytestream_put_byte(bytestream, 0x3b);
126  return 0;
127 }
128 
130 {
131  GIFContext *s = avctx->priv_data;
132 
133  avctx->coded_frame = &s->picture;
135  if (!s->lzw)
136  return AVERROR(ENOMEM);
137  s->buf = av_malloc(avctx->width*avctx->height*2);
138  if (!s->buf)
139  return AVERROR(ENOMEM);
140  return 0;
141 }
142 
143 /* better than nothing gif encoder */
144 static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)
145 {
146  GIFContext *s = avctx->priv_data;
147  AVFrame *pict = data;
148  AVFrame *const p = (AVFrame *)&s->picture;
149  uint8_t *outbuf_ptr = outbuf;
150  uint8_t *end = outbuf + buf_size;
151 
152  *p = *pict;
154  p->key_frame = 1;
155  gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
156  gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
157  return outbuf_ptr - outbuf;
158 }
159 
161 {
162  GIFContext *s = avctx->priv_data;
163 
164  av_freep(&s->lzw);
165  av_freep(&s->buf);
166  return 0;
167 }
168 
170  .name = "gif",
171  .type = AVMEDIA_TYPE_VIDEO,
172  .id = CODEC_ID_GIF,
173  .priv_data_size = sizeof(GIFContext),
175  .encode = gif_encode_frame,
178  .long_name= NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
179 };
void * av_mallocz(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:154
int size
Audio Video Frame.
Definition: avcodec.h:985
static int gif_image_write_image(AVCodecContext *avctx, uint8_t **bytestream, uint8_t *end, const uint8_t *buf, int linesize)
Definition: gif.c:85
AVFrame * coded_frame
the picture in the bitstream
Definition: avcodec.h:2000
static int gif_encode_close(AVCodecContext *avctx)
Definition: gif.c:160
int ff_lzw_encode(struct LZWEncodeState *s, const uint8_t *inbuf, int insize)
LZW main compress function.
Definition: lzwenc.c:226
AVCodec ff_gif_encoder
Definition: gif.c:169
AVCodec.
Definition: avcodec.h:3189
#define v(n)
Definition: regs.h:34
void av_freep(void *arg)
Free a memory block which has been allocated with av_malloc(z)() or av_realloc() and set the pointer ...
Definition: mem.c:147
packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb)
Definition: pixfmt.h:86
#define av_cold
Definition: attributes.h:71
const char data[16]
Definition: mxf.c:60
static int init(AVCodecParserContext *s)
Definition: h264_parser.c:336
int ff_lzw_encode_flush(struct LZWEncodeState *s, void(*lzw_flush_put_bits)(struct PutBitContext *))
Definition: lzw.c:44
LZWState * lzw
Definition: gif.c:56
#define AVERROR(e)
Definition: error.h:43
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:191
Definition: gif.c:54
const char * name
Name of the codec implementation.
Definition: avcodec.h:3196
static void put_bits(PutBitContext *s, int n, unsigned int value)
Write up to 31 bits into a bitstream.
Definition: put_bits.h:136
static int gif_encode_frame(AVCodecContext *avctx, unsigned char *outbuf, int buf_size, void *data)
Definition: gif.c:144
packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb)
Definition: pixfmt.h:85
enum AVPictureType pict_type
Picture type of the frame, see ?_TYPE below.
Definition: avcodec.h:1029
#define FFMIN(a, b)
Definition: common.h:55
Definition: lzw.h:38
packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb)
Definition: pixfmt.h:88
int width
picture width / height.
Definition: avcodec.h:1408
static int gif_image_write_header(AVCodecContext *avctx, uint8_t **bytestream, uint32_t *palette)
Definition: gif.c:61
external API header
int linesize[AV_NUM_DATA_POINTERS]
Size, in bytes, of the data for each picture/channel plane.
Definition: avcodec.h:1008
main external API structure.
Definition: avcodec.h:1329
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:327
void * av_malloc(size_t size)
Allocate a block of size bytes with alignment suitable for all memory accesses (including vectors if ...
Definition: mem.c:64
packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb)
Definition: pixfmt.h:83
uint8_t * buf
Definition: gif.c:57
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: avcodec.h:997
int height
Definition: gxfenc.c:73
LZW decoding routines.
int palette
Definition: v4l.c:63
PixelFormat
Pixel format.
Definition: pixfmt.h:62
void ff_lzw_encode_init(struct LZWEncodeState *s, uint8_t *outbuf, int outsize, int maxbits, enum FF_LZW_MODES mode, void(*lzw_put_bits)(struct PutBitContext *, int, unsigned int))
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:86
8 bit with PIX_FMT_RGB32 palette
Definition: pixfmt.h:75
static av_always_inline void bytestream_put_buffer(uint8_t **b, const uint8_t *src, unsigned int size)
Definition: bytestream.h:371
void * priv_data
Definition: avcodec.h:1531
int len
static av_cold int gif_encode_init(AVCodecContext *avctx)
Definition: gif.c:129
int key_frame
1 -> keyframe, 0-> not
Definition: avcodec.h:1022
const int ff_lzw_encode_state_size
Definition: lzwenc.c:66
Y , 8bpp.
Definition: pixfmt.h:72
AVFrame picture
Definition: gif.c:55
bitstream writer API