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 "internal.h"
47 #include "lzw.h"
48 
49 /* The GIF format uses reversed order for bitstreams... */
50 /* at least they don't use PDP_ENDIAN :) */
51 #define BITSTREAM_WRITER_LE
52 
53 #include "put_bits.h"
54 
55 typedef struct {
59 } GIFContext;
60 
61 /* GIF header */
63  uint8_t **bytestream, uint32_t *palette)
64 {
65  int i;
66  unsigned int v;
67 
68  bytestream_put_buffer(bytestream, "GIF", 3);
69  bytestream_put_buffer(bytestream, "89a", 3);
70  bytestream_put_le16(bytestream, avctx->width);
71  bytestream_put_le16(bytestream, avctx->height);
72 
73  bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
74  bytestream_put_byte(bytestream, 0x1f); /* background color index */
75  bytestream_put_byte(bytestream, 0); /* aspect ratio */
76 
77  /* the global palette */
78  for(i=0;i<256;i++) {
79  v = palette[i];
80  bytestream_put_be24(bytestream, v);
81  }
82 
83  return 0;
84 }
85 
87  uint8_t **bytestream, uint8_t *end,
88  const uint8_t *buf, int linesize)
89 {
90  GIFContext *s = avctx->priv_data;
91  int len = 0, height;
92  const uint8_t *ptr;
93  /* image block */
94 
95  bytestream_put_byte(bytestream, 0x2c);
96  bytestream_put_le16(bytestream, 0);
97  bytestream_put_le16(bytestream, 0);
98  bytestream_put_le16(bytestream, avctx->width);
99  bytestream_put_le16(bytestream, avctx->height);
100  bytestream_put_byte(bytestream, 0x00); /* flags */
101  /* no local clut */
102 
103  bytestream_put_byte(bytestream, 0x08);
104 
105  ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,
106  12, FF_LZW_GIF, put_bits);
107 
108  ptr = buf;
109  for (height = avctx->height; height--;) {
110  len += ff_lzw_encode(s->lzw, ptr, avctx->width);
111  ptr += linesize;
112  }
114 
115  ptr = s->buf;
116  while (len > 0) {
117  int size = FFMIN(255, len);
118  bytestream_put_byte(bytestream, size);
119  if (end - *bytestream < size)
120  return -1;
121  bytestream_put_buffer(bytestream, ptr, size);
122  ptr += size;
123  len -= size;
124  }
125  bytestream_put_byte(bytestream, 0x00); /* end of image block */
126  bytestream_put_byte(bytestream, 0x3b);
127  return 0;
128 }
129 
131 {
132  GIFContext *s = avctx->priv_data;
133 
134  avctx->coded_frame = &s->picture;
136  if (!s->lzw)
137  return AVERROR(ENOMEM);
138  s->buf = av_malloc(avctx->width*avctx->height*2);
139  if (!s->buf)
140  return AVERROR(ENOMEM);
141  return 0;
142 }
143 
144 /* better than nothing gif encoder */
145 static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
146  const AVFrame *pict, int *got_packet)
147 {
148  GIFContext *s = avctx->priv_data;
149  AVFrame *const p = &s->picture;
150  uint8_t *outbuf_ptr, *end;
151  int ret;
152 
153  if ((ret = ff_alloc_packet(pkt, avctx->width*avctx->height*7/5 + FF_MIN_BUFFER_SIZE)) < 0) {
154  av_log(avctx, AV_LOG_ERROR, "Error getting output packet.\n");
155  return ret;
156  }
157  outbuf_ptr = pkt->data;
158  end = pkt->data + pkt->size;
159 
160  *p = *pict;
162  p->key_frame = 1;
163  gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
164  gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
165 
166  pkt->size = outbuf_ptr - pkt->data;
167  pkt->flags |= AV_PKT_FLAG_KEY;
168  *got_packet = 1;
169 
170  return 0;
171 }
172 
174 {
175  GIFContext *s = avctx->priv_data;
176 
177  av_freep(&s->lzw);
178  av_freep(&s->buf);
179  return 0;
180 }
181 
183  .name = "gif",
184  .type = AVMEDIA_TYPE_VIDEO,
185  .id = AV_CODEC_ID_GIF,
186  .priv_data_size = sizeof(GIFContext),
188  .encode2 = gif_encode_frame,
190  .pix_fmts = (const enum AVPixelFormat[]){
193  },
194  .long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
195 };
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:61
int size
This structure describes decoded (raw) audio or video data.
Definition: avcodec.h:989
static int gif_image_write_image(AVCodecContext *avctx, uint8_t **bytestream, uint8_t *end, const uint8_t *buf, int linesize)
Definition: gif.c:86
AVFrame * coded_frame
the picture in the bitstream
Definition: avcodec.h:2725
int size
Definition: avcodec.h:916
static int gif_encode_close(AVCodecContext *avctx)
Definition: gif.c:173
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:182
AVCodec.
Definition: avcodec.h:2960
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:151
packed RGB 1:2:1, 8bpp, (msb)1B 2G 1R(lsb)
Definition: pixfmt.h:86
uint8_t
8 bit with PIX_FMT_RGB32 palette
Definition: pixfmt.h:76
uint8_t * data
Definition: avcodec.h:915
static int init(AVCodecParserContext *s)
Definition: h264_parser.c:335
int ff_lzw_encode_flush(struct LZWEncodeState *s, void(*lzw_flush_put_bits)(struct PutBitContext *))
Definition: lzw.c:46
LZWState * lzw
Definition: gif.c:57
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:88
Definition: gif.c:55
void av_log(void *avcl, int level, const char *fmt,...)
Definition: log.c:146
const char * name
Name of the codec implementation.
Definition: avcodec.h:2967
static void put_bits(PutBitContext *s, int n, unsigned int value)
Write up to 31 bits into a bitstream.
Definition: put_bits.h:136
int flags
A combination of AV_PKT_FLAG values.
Definition: avcodec.h:921
enum AVPictureType pict_type
Picture type of the frame, see ?_TYPE below.
Definition: avcodec.h:1065
Definition: lzw.h:38
packed RGB 1:2:1, 8bpp, (msb)1R 2G 1B(lsb)
Definition: pixfmt.h:89
int width
picture width / height.
Definition: avcodec.h:1508
static int gif_image_write_header(AVCodecContext *avctx, uint8_t **bytestream, uint32_t *palette)
Definition: gif.c:62
int ff_alloc_packet(AVPacket *avpkt, int size)
Check AVPacket size and/or allocate data.
Definition: utils.c:878
packed RGB 3:3:2, 8bpp, (msb)2B 3G 3R(lsb)
Definition: pixfmt.h:84
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:1339
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:326
static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt, const AVFrame *pict, int *got_packet)
Definition: gif.c:145
uint8_t * buf
Definition: gif.c:58
uint8_t * data[AV_NUM_DATA_POINTERS]
pointer to the picture/channel planes.
Definition: avcodec.h:997
int height
Definition: gxfenc.c:72
LZW decoding routines.
Y , 8bpp.
Definition: pixfmt.h:73
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))
common internal api header.
static void flush_put_bits(PutBitContext *s)
Pad the end of the output stream with zeros.
Definition: put_bits.h:86
packed RGB 3:3:2, 8bpp, (msb)2R 3G 3B(lsb)
Definition: pixfmt.h:87
static av_always_inline void bytestream_put_buffer(uint8_t **b, const uint8_t *src, unsigned int size)
Definition: bytestream.h:327
void * priv_data
Definition: avcodec.h:1382
int len
static av_cold int gif_encode_init(AVCodecContext *avctx)
Definition: gif.c:130
int key_frame
1 -> keyframe, 0-> not
Definition: avcodec.h:1058
const int ff_lzw_encode_state_size
Definition: lzwenc.c:66
AVFrame picture
Definition: gif.c:56
AVPixelFormat
Pixel format.
Definition: pixfmt.h:63
This structure stores compressed data.
Definition: avcodec.h:898
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:158
bitstream writer API