1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
|
/*
* GIF encoder.
* Copyright (c) 2000 Fabrice Bellard
* Copyright (c) 2002 Francois Revol
* Copyright (c) 2006 Baptiste Coudurier
*
* This file is part of FFmpeg.
*
* FFmpeg is free software; you can redistribute it and/or
* modify it under the terms of the GNU Lesser General Public
* License as published by the Free Software Foundation; either
* version 2.1 of the License, or (at your option) any later version.
*
* FFmpeg is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with FFmpeg; if not, write to the Free Software
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
/*
* First version by Francois Revol revol@free.fr
*
* Features and limitations:
* - currently no compression is performed,
* in fact the size of the data is 9/8 the size of the image in 8bpp
* - uses only a global standard palette
* - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
*
* Reference documents:
* http://www.goice.co.jp/member/mo/formats/gif.html
* http://astronomy.swin.edu.au/pbourke/dataformats/gif/
* http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
*
* this url claims to have an LZW algorithm not covered by Unisys patent:
* http://www.msg.net/utility/whirlgif/gifencod.html
* could help reduce the size of the files _a lot_...
* some sites mentions an RLE type compression also.
*/
#include "avcodec.h"
#include "bytestream.h"
#include "internal.h"
#include "lzw.h"
/* The GIF format uses reversed order for bitstreams... */
/* at least they don't use PDP_ENDIAN :) */
#define BITSTREAM_WRITER_LE
#include "put_bits.h"
typedef struct {
AVFrame picture;
LZWState *lzw;
uint8_t *buf;
} GIFContext;
/* GIF header */
static int gif_image_write_header(AVCodecContext *avctx,
uint8_t **bytestream, uint32_t *palette)
{
int i;
unsigned int v, smallest_alpha = 0xFF, alpha_component = 0;
bytestream_put_buffer(bytestream, "GIF", 3);
bytestream_put_buffer(bytestream, "89a", 3);
bytestream_put_le16(bytestream, avctx->width);
bytestream_put_le16(bytestream, avctx->height);
bytestream_put_byte(bytestream, 0xf7); /* flags: global clut, 256 entries */
bytestream_put_byte(bytestream, 0x1f); /* background color index */
bytestream_put_byte(bytestream, 0); /* aspect ratio */
/* the global palette */
for(i=0;i<256;i++) {
v = palette[i];
bytestream_put_be24(bytestream, v);
if (v >> 24 < smallest_alpha) {
smallest_alpha = v >> 24;
alpha_component = i;
}
}
if (smallest_alpha < 128) {
bytestream_put_byte(bytestream, 0x21); /* Extension Introducer */
bytestream_put_byte(bytestream, 0xf9); /* Graphic Control Label */
bytestream_put_byte(bytestream, 0x04); /* block length */
bytestream_put_byte(bytestream, 0x01); /* Transparent Color Flag */
bytestream_put_le16(bytestream, 0x00); /* no delay */
bytestream_put_byte(bytestream, alpha_component);
bytestream_put_byte(bytestream, 0x00);
}
return 0;
}
static int gif_image_write_image(AVCodecContext *avctx,
uint8_t **bytestream, uint8_t *end,
const uint8_t *buf, int linesize)
{
GIFContext *s = avctx->priv_data;
int len = 0, height;
const uint8_t *ptr;
/* image block */
bytestream_put_byte(bytestream, 0x2c);
bytestream_put_le16(bytestream, 0);
bytestream_put_le16(bytestream, 0);
bytestream_put_le16(bytestream, avctx->width);
bytestream_put_le16(bytestream, avctx->height);
bytestream_put_byte(bytestream, 0x00); /* flags */
/* no local clut */
bytestream_put_byte(bytestream, 0x08);
ff_lzw_encode_init(s->lzw, s->buf, avctx->width*avctx->height,
12, FF_LZW_GIF, put_bits);
ptr = buf;
for (height = avctx->height; height--;) {
len += ff_lzw_encode(s->lzw, ptr, avctx->width);
ptr += linesize;
}
len += ff_lzw_encode_flush(s->lzw, flush_put_bits);
ptr = s->buf;
while (len > 0) {
int size = FFMIN(255, len);
bytestream_put_byte(bytestream, size);
if (end - *bytestream < size)
return -1;
bytestream_put_buffer(bytestream, ptr, size);
ptr += size;
len -= size;
}
bytestream_put_byte(bytestream, 0x00); /* end of image block */
bytestream_put_byte(bytestream, 0x3b);
return 0;
}
static av_cold int gif_encode_init(AVCodecContext *avctx)
{
GIFContext *s = avctx->priv_data;
if (avctx->width > 65535 || avctx->height > 65535) {
av_log(avctx, AV_LOG_ERROR, "GIF does not support resolutions above 65535x65535\n");
return -1;
}
avctx->coded_frame = &s->picture;
s->lzw = av_mallocz(ff_lzw_encode_state_size);
if (!s->lzw)
return AVERROR(ENOMEM);
s->buf = av_malloc(avctx->width*avctx->height*2);
if (!s->buf)
return AVERROR(ENOMEM);
return 0;
}
/* better than nothing gif encoder */
static int gif_encode_frame(AVCodecContext *avctx, AVPacket *pkt,
const AVFrame *pict, int *got_packet)
{
GIFContext *s = avctx->priv_data;
AVFrame *const p = &s->picture;
uint8_t *outbuf_ptr, *end;
int ret;
if ((ret = ff_alloc_packet2(avctx, pkt, avctx->width*avctx->height*7/5 + FF_MIN_BUFFER_SIZE)) < 0)
return ret;
outbuf_ptr = pkt->data;
end = pkt->data + pkt->size;
*p = *pict;
p->pict_type = AV_PICTURE_TYPE_I;
p->key_frame = 1;
gif_image_write_header(avctx, &outbuf_ptr, (uint32_t *)pict->data[1]);
gif_image_write_image(avctx, &outbuf_ptr, end, pict->data[0], pict->linesize[0]);
pkt->size = outbuf_ptr - pkt->data;
pkt->flags |= AV_PKT_FLAG_KEY;
*got_packet = 1;
return 0;
}
static int gif_encode_close(AVCodecContext *avctx)
{
GIFContext *s = avctx->priv_data;
av_freep(&s->lzw);
av_freep(&s->buf);
return 0;
}
AVCodec ff_gif_encoder = {
.name = "gif",
.type = AVMEDIA_TYPE_VIDEO,
.id = AV_CODEC_ID_GIF,
.priv_data_size = sizeof(GIFContext),
.init = gif_encode_init,
.encode2 = gif_encode_frame,
.close = gif_encode_close,
.pix_fmts = (const enum AVPixelFormat[]){
AV_PIX_FMT_RGB8, AV_PIX_FMT_BGR8, AV_PIX_FMT_RGB4_BYTE, AV_PIX_FMT_BGR4_BYTE,
AV_PIX_FMT_GRAY8, AV_PIX_FMT_PAL8, AV_PIX_FMT_NONE
},
.long_name = NULL_IF_CONFIG_SMALL("GIF (Graphics Interchange Format)"),
};
|
