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  int i;
35 
36  avio_write(pb, "GIF", 3);
37  avio_write(pb, "89a", 3);
38  avio_wl16(pb, width);
39  avio_wl16(pb, height);
40 
41  if (palette) {
42  avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
43  avio_w8(pb, 0x1f); /* background color index */
44  avio_w8(pb, 0); /* aspect ratio */
45  for (i = 0; i < 256; i++) {
46  const uint32_t v = palette[i] & 0xffffff;
47  avio_wb24(pb, v);
48  }
49  } else {
50  avio_w8(pb, 0); /* flags */
51  avio_w8(pb, 0); /* background color index */
52  avio_w8(pb, 0); /* aspect ratio */
53  }
54 
55 
56  if (loop_count >= 0 ) {
57  /* "NETSCAPE EXTENSION" for looped animation GIF */
58  avio_w8(pb, 0x21); /* GIF Extension code */
59  avio_w8(pb, 0xff); /* Application Extension Label */
60  avio_w8(pb, 0x0b); /* Length of Application Block */
61  avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
62  avio_w8(pb, 0x03); /* Length of Data Sub-Block */
63  avio_w8(pb, 0x01);
64  avio_wl16(pb, (uint16_t)loop_count);
65  avio_w8(pb, 0x00); /* Data Sub-block Terminator */
66  }
67 
68  return 0;
69 }
70 
71 typedef struct {
72  AVClass *class;
73  int loop;
76  int duration;
77 } GIFContext;
78 
80 {
81  GIFContext *gif = s->priv_data;
82  AVIOContext *pb = s->pb;
83  AVCodecContext *video_enc;
84  int width, height;
85  uint32_t palette[AVPALETTE_COUNT];
86 
87  if (s->nb_streams != 1 ||
91  "GIF muxer supports only a single video GIF stream.\n");
92  return AVERROR(EINVAL);
93  }
94 
95  video_enc = s->streams[0]->codec;
96  width = video_enc->width;
97  height = video_enc->height;
98 
99  avpriv_set_pts_info(s->streams[0], 64, 1, 100);
100  if (avpriv_set_systematic_pal2(palette, video_enc->pix_fmt) < 0) {
101  av_assert0(video_enc->pix_fmt == AV_PIX_FMT_PAL8);
102  gif_image_write_header(pb, width, height, gif->loop, NULL);
103  } else {
104  gif_image_write_header(pb, width, height, gif->loop, palette);
105  }
106 
107  avio_flush(s->pb);
108  return 0;
109 }
110 
112 {
113  GIFContext *gif = s->priv_data;
114  int size;
115  AVIOContext *pb = s->pb;
116  uint8_t flags = 0x4, transparent_color_index = 0x1f;
117  const uint32_t *palette;
118  AVPacket *pkt = gif->prev_pkt;
119 
120  if (!pkt)
121  return 0;
122 
123  /* Mark one colour as transparent if the input palette contains at least
124  * one colour that is more than 50% transparent. */
125  palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
126  if (palette && size != AVPALETTE_SIZE) {
127  av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
128  return AVERROR_INVALIDDATA;
129  }
130  if (palette) {
131  unsigned i, smallest_alpha = 0xff;
132 
133  for (i = 0; i < AVPALETTE_COUNT; i++) {
134  const uint32_t v = palette[i];
135  if (v >> 24 < smallest_alpha) {
136  smallest_alpha = v >> 24;
137  transparent_color_index = i;
138  }
139  }
140  if (smallest_alpha < 128)
141  flags |= 0x1; /* Transparent Color Flag */
142  }
143 
144  if (new && new->pts != AV_NOPTS_VALUE)
145  gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts);
146  else if (!new && gif->last_delay >= 0)
147  gif->duration = gif->last_delay;
148 
149  /* graphic control extension block */
150  avio_w8(pb, 0x21);
151  avio_w8(pb, 0xf9);
152  avio_w8(pb, 0x04); /* block size */
153  avio_w8(pb, flags);
154  avio_wl16(pb, gif->duration);
155  avio_w8(pb, transparent_color_index);
156  avio_w8(pb, 0x00);
157 
158  avio_write(pb, pkt->data, pkt->size);
159 
160  av_free_packet(gif->prev_pkt);
161  if (new)
162  av_copy_packet(gif->prev_pkt, new);
163 
164  return 0;
165 }
166 
168 {
169  GIFContext *gif = s->priv_data;
170 
171  if (!gif->prev_pkt) {
172  gif->prev_pkt = av_malloc(sizeof(*gif->prev_pkt));
173  if (!gif->prev_pkt)
174  return AVERROR(ENOMEM);
175  return av_copy_packet(gif->prev_pkt, pkt);
176  }
177  return flush_packet(s, pkt);
178 }
179 
181 {
182  GIFContext *gif = s->priv_data;
183  AVIOContext *pb = s->pb;
184 
185  flush_packet(s, NULL);
186  av_freep(&gif->prev_pkt);
187  avio_w8(pb, 0x3b);
188 
189  return 0;
190 }
191 
192 #define OFFSET(x) offsetof(GIFContext, x)
193 #define ENC AV_OPT_FLAG_ENCODING_PARAM
194 static const AVOption options[] = {
195  { "loop", "Number of times to loop the output: -1 - no loop, 0 - infinite loop", OFFSET(loop),
196  AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
197  { "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
198  AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, ENC },
199  { NULL },
200 };
201 
202 static const AVClass gif_muxer_class = {
203  .class_name = "GIF muxer",
204  .item_name = av_default_item_name,
205  .version = LIBAVUTIL_VERSION_INT,
206  .option = options,
207 };
208 
210  .name = "gif",
211  .long_name = NULL_IF_CONFIG_SMALL("GIF Animation"),
212  .mime_type = "image/gif",
213  .extensions = "gif",
214  .priv_data_size = sizeof(GIFContext),
215  .audio_codec = AV_CODEC_ID_NONE,
216  .video_codec = AV_CODEC_ID_GIF,
220  .priv_class = &gif_muxer_class,
222 };