FFmpeg
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gif.c
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1 /*
2  * Animated GIF muxer
3  * Copyright (c) 2000 Fabrice Bellard
4  *
5  * first version by Francois Revol <revol@free.fr>
6  *
7  * This file is part of FFmpeg.
8  *
9  * FFmpeg 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  * FFmpeg 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 FFmpeg; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 #include "avformat.h"
25 #include "internal.h"
26 #include "libavutil/avassert.h"
27 #include "libavutil/imgutils.h"
28 #include "libavutil/log.h"
29 #include "libavutil/opt.h"
30 
32  int loop_count, uint32_t *palette)
33 {
34  AVIOContext *pb = s->pb;
36  int i;
37  int64_t aspect = 0;
38 
39  if (sar.num > 0 && sar.den > 0) {
40  aspect = sar.num * 64LL / sar.den - 15;
41  if (aspect < 0 || aspect > 255)
42  aspect = 0;
43  }
44 
45  avio_write(pb, "GIF", 3);
46  avio_write(pb, "89a", 3);
47  avio_wl16(pb, width);
48  avio_wl16(pb, height);
49 
50  if (palette) {
51  avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
52  avio_w8(pb, 0x1f); /* background color index */
53  avio_w8(pb, aspect);
54  for (i = 0; i < 256; i++) {
55  const uint32_t v = palette[i] & 0xffffff;
56  avio_wb24(pb, v);
57  }
58  } else {
59  avio_w8(pb, 0); /* flags */
60  avio_w8(pb, 0); /* background color index */
61  avio_w8(pb, aspect);
62  }
63 
64 
65  if (loop_count >= 0 ) {
66  /* "NETSCAPE EXTENSION" for looped animation GIF */
67  avio_w8(pb, 0x21); /* GIF Extension code */
68  avio_w8(pb, 0xff); /* Application Extension Label */
69  avio_w8(pb, 0x0b); /* Length of Application Block */
70  avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
71  avio_w8(pb, 0x03); /* Length of Data Sub-Block */
72  avio_w8(pb, 0x01);
73  avio_wl16(pb, (uint16_t)loop_count);
74  avio_w8(pb, 0x00); /* Data Sub-block Terminator */
75  }
76 
77  return 0;
78 }
79 
80 typedef struct {
81  AVClass *class;
82  int loop;
85  int duration;
86 } GIFContext;
87 
89 {
90  GIFContext *gif = s->priv_data;
91  AVCodecContext *video_enc;
92  int width, height;
93  uint32_t palette[AVPALETTE_COUNT];
94 
95  if (s->nb_streams != 1 ||
99  "GIF muxer supports only a single video GIF stream.\n");
100  return AVERROR(EINVAL);
101  }
102 
103  video_enc = s->streams[0]->codec;
104  width = video_enc->width;
105  height = video_enc->height;
106 
107  avpriv_set_pts_info(s->streams[0], 64, 1, 100);
108  if (avpriv_set_systematic_pal2(palette, video_enc->pix_fmt) < 0) {
109  av_assert0(video_enc->pix_fmt == AV_PIX_FMT_PAL8);
110  gif_image_write_header(s, width, height, gif->loop, NULL);
111  } else {
112  gif_image_write_header(s, width, height, gif->loop, palette);
113  }
114 
115  avio_flush(s->pb);
116  return 0;
117 }
118 
120 {
121  GIFContext *gif = s->priv_data;
122  int size;
123  AVIOContext *pb = s->pb;
124  uint8_t flags = 0x4, transparent_color_index = 0x1f;
125  const uint32_t *palette;
126  AVPacket *pkt = gif->prev_pkt;
127 
128  if (!pkt)
129  return 0;
130 
131  /* Mark one colour as transparent if the input palette contains at least
132  * one colour that is more than 50% transparent. */
133  palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
134  if (palette && size != AVPALETTE_SIZE) {
135  av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
136  return AVERROR_INVALIDDATA;
137  }
138  if (palette) {
139  unsigned i, smallest_alpha = 0xff;
140 
141  for (i = 0; i < AVPALETTE_COUNT; i++) {
142  const uint32_t v = palette[i];
143  if (v >> 24 < smallest_alpha) {
144  smallest_alpha = v >> 24;
145  transparent_color_index = i;
146  }
147  }
148  if (smallest_alpha < 128)
149  flags |= 0x1; /* Transparent Color Flag */
150  }
151 
152  if (new && new->pts != AV_NOPTS_VALUE)
153  gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts);
154  else if (!new && gif->last_delay >= 0)
155  gif->duration = gif->last_delay;
156 
157  /* graphic control extension block */
158  avio_w8(pb, 0x21);
159  avio_w8(pb, 0xf9);
160  avio_w8(pb, 0x04); /* block size */
161  avio_w8(pb, flags);
162  avio_wl16(pb, gif->duration);
163  avio_w8(pb, transparent_color_index);
164  avio_w8(pb, 0x00);
165 
166  avio_write(pb, pkt->data, pkt->size);
167 
168  av_free_packet(gif->prev_pkt);
169  if (new)
170  av_copy_packet(gif->prev_pkt, new);
171 
172  return 0;
173 }
174 
176 {
177  GIFContext *gif = s->priv_data;
178 
179  if (!gif->prev_pkt) {
180  gif->prev_pkt = av_malloc(sizeof(*gif->prev_pkt));
181  if (!gif->prev_pkt)
182  return AVERROR(ENOMEM);
183  return av_copy_packet(gif->prev_pkt, pkt);
184  }
185  return flush_packet(s, pkt);
186 }
187 
189 {
190  GIFContext *gif = s->priv_data;
191  AVIOContext *pb = s->pb;
192 
193  flush_packet(s, NULL);
194  av_freep(&gif->prev_pkt);
195  avio_w8(pb, 0x3b);
196 
197  return 0;
198 }
199 
200 #define OFFSET(x) offsetof(GIFContext, x)
201 #define ENC AV_OPT_FLAG_ENCODING_PARAM
202 static const AVOption options[] = {
203  { "loop", "Number of times to loop the output: -1 - no loop, 0 - infinite loop", OFFSET(loop),
204  AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
205  { "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
206  AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, ENC },
207  { NULL },
208 };
209 
210 static const AVClass gif_muxer_class = {
211  .class_name = "GIF muxer",
212  .item_name = av_default_item_name,
213  .version = LIBAVUTIL_VERSION_INT,
214  .option = options,
215 };
216 
218  .name = "gif",
219  .long_name = NULL_IF_CONFIG_SMALL("GIF Animation"),
220  .mime_type = "image/gif",
221  .extensions = "gif",
222  .priv_data_size = sizeof(GIFContext),
223  .audio_codec = AV_CODEC_ID_NONE,
224  .video_codec = AV_CODEC_ID_GIF,
228  .priv_class = &gif_muxer_class,
230 };