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/*

 * Animated GIF muxer

 * Copyright (c) 2000 Fabrice Bellard

 *

 * first version by Francois Revol 

 *

 * 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(AVIOContext *pb, int width, int height,

                                  int loop_count, uint32_t *palette)

{

    int i;

    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, 0);    /* aspect ratio */

        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, 0); /* aspect ratio */

    }

    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;

    AVIOContext *pb = s->pb;

    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(pb, width, height, gif->loop, NULL);

    } else {

        gif_image_write_header(pb, 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 ms) 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,

};