summaryrefslogtreecommitdiffstats
path: root/libavformat/gif.c
blob: e81712144000a23edaa01c702a5fe83c507976a0 (plain)
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
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
/*
 * Animated GIF muxer
 * Copyright (c) 2000 Fabrice Bellard
 *
 * first version by Francois Revol <revol@free.fr>
 *
 * 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
 */

#include "avformat.h"
#include "internal.h"
#include "libavutil/avassert.h"
#include "libavutil/imgutils.h"
#include "libavutil/log.h"
#include "libavutil/opt.h"

static int gif_image_write_header(AVFormatContext *s, int width, int height,
                                  int loop_count, uint32_t *palette)
{
    AVIOContext *pb = s->pb;
    AVRational sar = s->streams[0]->codec->sample_aspect_ratio;
    int i;
    int64_t aspect = 0;

    if (sar.num > 0 && sar.den > 0) {
        aspect = sar.num * 64LL / sar.den - 15;
        if (aspect < 0 || aspect > 255)
            aspect = 0;
    }

    avio_write(pb, "GIF", 3);
    avio_write(pb, "89a", 3);
    avio_wl16(pb, width);
    avio_wl16(pb, height);

    if (palette) {
        avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */
        avio_w8(pb, 0x1f); /* background color index */
        avio_w8(pb, aspect);
        for (i = 0; i < 256; i++) {
            const uint32_t v = palette[i] & 0xffffff;
            avio_wb24(pb, v);
        }
    } else {
        avio_w8(pb, 0); /* flags */
        avio_w8(pb, 0); /* background color index */
        avio_w8(pb, aspect);
    }


    if (loop_count >= 0 ) {
        /* "NETSCAPE EXTENSION" for looped animation GIF */
        avio_w8(pb, 0x21); /* GIF Extension code */
        avio_w8(pb, 0xff); /* Application Extension Label */
        avio_w8(pb, 0x0b); /* Length of Application Block */
        avio_write(pb, "NETSCAPE2.0", sizeof("NETSCAPE2.0") - 1);
        avio_w8(pb, 0x03); /* Length of Data Sub-Block */
        avio_w8(pb, 0x01);
        avio_wl16(pb, (uint16_t)loop_count);
        avio_w8(pb, 0x00); /* Data Sub-block Terminator */
    }

    return 0;
}

typedef struct {
    AVClass *class;
    int loop;
    int last_delay;
    AVPacket *prev_pkt;
    int duration;
} GIFContext;

static int gif_write_header(AVFormatContext *s)
{
    GIFContext *gif = s->priv_data;
    AVCodecContext *video_enc;
    int width, height;
    uint32_t palette[AVPALETTE_COUNT];

    if (s->nb_streams != 1 ||
        s->streams[0]->codec->codec_type != AVMEDIA_TYPE_VIDEO ||
        s->streams[0]->codec->codec_id   != AV_CODEC_ID_GIF) {
        av_log(s, AV_LOG_ERROR,
               "GIF muxer supports only a single video GIF stream.\n");
        return AVERROR(EINVAL);
    }

    video_enc = s->streams[0]->codec;
    width  = video_enc->width;
    height = video_enc->height;

    avpriv_set_pts_info(s->streams[0], 64, 1, 100);
    if (avpriv_set_systematic_pal2(palette, video_enc->pix_fmt) < 0) {
        av_assert0(video_enc->pix_fmt == AV_PIX_FMT_PAL8);
        gif_image_write_header(s, width, height, gif->loop, NULL);
    } else {
        gif_image_write_header(s, width, height, gif->loop, palette);
    }

    avio_flush(s->pb);
    return 0;
}

static int flush_packet(AVFormatContext *s, AVPacket *new)
{
    GIFContext *gif = s->priv_data;
    int size;
    AVIOContext *pb = s->pb;
    uint8_t flags = 0x4, transparent_color_index = 0x1f;
    const uint32_t *palette;
    AVPacket *pkt = gif->prev_pkt;

    if (!pkt)
        return 0;

    /* Mark one colour as transparent if the input palette contains at least
     * one colour that is more than 50% transparent. */
    palette = (uint32_t*)av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
    if (palette && size != AVPALETTE_SIZE) {
        av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
        return AVERROR_INVALIDDATA;
    }
    if (palette) {
        unsigned i, smallest_alpha = 0xff;

        for (i = 0; i < AVPALETTE_COUNT; i++) {
            const uint32_t v = palette[i];
            if (v >> 24 < smallest_alpha) {
                smallest_alpha = v >> 24;
                transparent_color_index = i;
            }
        }
        if (smallest_alpha < 128)
            flags |= 0x1; /* Transparent Color Flag */
    }

    if (new && new->pts != AV_NOPTS_VALUE)
        gif->duration = av_clip_uint16(new->pts - gif->prev_pkt->pts);
    else if (!new && gif->last_delay >= 0)
        gif->duration = gif->last_delay;

    /* graphic control extension block */
    avio_w8(pb, 0x21);
    avio_w8(pb, 0xf9);
    avio_w8(pb, 0x04); /* block size */
    avio_w8(pb, flags);
    avio_wl16(pb, gif->duration);
    avio_w8(pb, transparent_color_index);
    avio_w8(pb, 0x00);

    avio_write(pb, pkt->data, pkt->size);

    av_free_packet(gif->prev_pkt);
    if (new)
        av_copy_packet(gif->prev_pkt, new);

    return 0;
}

static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
{
    GIFContext *gif = s->priv_data;

    if (!gif->prev_pkt) {
        gif->prev_pkt = av_malloc(sizeof(*gif->prev_pkt));
        if (!gif->prev_pkt)
            return AVERROR(ENOMEM);
        return av_copy_packet(gif->prev_pkt, pkt);
    }
    return flush_packet(s, pkt);
}

static int gif_write_trailer(AVFormatContext *s)
{
    GIFContext *gif = s->priv_data;
    AVIOContext *pb = s->pb;

    flush_packet(s, NULL);
    av_freep(&gif->prev_pkt);
    avio_w8(pb, 0x3b);

    return 0;
}

#define OFFSET(x) offsetof(GIFContext, x)
#define ENC AV_OPT_FLAG_ENCODING_PARAM
static const AVOption options[] = {
    { "loop", "Number of times to loop the output: -1 - no loop, 0 - infinite loop", OFFSET(loop),
      AV_OPT_TYPE_INT, { .i64 = 0 }, -1, 65535, ENC },
    { "final_delay", "Force delay (in centiseconds) after the last frame", OFFSET(last_delay),
      AV_OPT_TYPE_INT, { .i64 = -1 }, -1, 65535, ENC },
    { NULL },
};

static const AVClass gif_muxer_class = {
    .class_name = "GIF muxer",
    .item_name  = av_default_item_name,
    .version    = LIBAVUTIL_VERSION_INT,
    .option     = options,
};

AVOutputFormat ff_gif_muxer = {
    .name           = "gif",
    .long_name      = NULL_IF_CONFIG_SMALL("GIF Animation"),
    .mime_type      = "image/gif",
    .extensions     = "gif",
    .priv_data_size = sizeof(GIFContext),
    .audio_codec    = AV_CODEC_ID_NONE,
    .video_codec    = AV_CODEC_ID_GIF,
    .write_header   = gif_write_header,
    .write_packet   = gif_write_packet,
    .write_trailer  = gif_write_trailer,
    .priv_class     = &gif_muxer_class,
    .flags          = AVFMT_VARIABLE_FPS,
};
OpenPOWER on IntegriCloud