/*

  * 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"

 /* XXX: random value that shouldn't be taken into effect if there is no
  * transparent color in the palette (the transparency bit will be set to 0) */
 #define DEFAULT_TRANSPARENCY_INDEX 0x1f
 
 static int get_palette_transparency_index(const uint32_t *palette)
 {
     int transparent_color_index = -1;
     unsigned i, smallest_alpha = 0xff;
 
     if (!palette)
         return -1;
 
     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;
         }
     }
     return smallest_alpha < 128 ? transparent_color_index : -1;
 }
 

 static int gif_image_write_header(AVIOContext *pb, const AVCodecContext *avctx,

                                   int loop_count, uint32_t *palette)

 {

     int i;
     int64_t aspect = 0;

     const AVRational sar = avctx->sample_aspect_ratio;

 
     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, avctx->width);
     avio_wl16(pb, avctx->height);

     if (palette) {

         const int bcid = get_palette_transparency_index(palette);
 

         avio_w8(pb, 0xf7); /* flags: global clut, 256 entries */

         avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid); /* 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 */
     }

     avio_flush(pb);

     return 0;
 }
 

 typedef struct GIFContext {

     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;

     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;

     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);

         /* delay header writing: we wait for the first palette to put it
          * globally */

     } else {

         gif_image_write_header(s->pb, video_enc, gif->loop, palette);

     }

 
     return 0;
 }
 

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

     int size, bcid;

     AVIOContext *pb = s->pb;

     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;
     }

     bcid = get_palette_transparency_index(palette);

     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, 1<<2 | (bcid >= 0));

     avio_wl16(pb, gif->duration);

     avio_w8(pb, bcid < 0 ? DEFAULT_TRANSPARENCY_INDEX : bcid);

     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;

     const AVCodecContext *video_enc = s->streams[0]->codec;

 
     if (!gif->prev_pkt) {
         gif->prev_pkt = av_malloc(sizeof(*gif->prev_pkt));
         if (!gif->prev_pkt)
             return AVERROR(ENOMEM);

 
         /* Write the first palette as global palette */
         if (video_enc->pix_fmt == AV_PIX_FMT_PAL8) {
             int size;
             void *palette = av_packet_get_side_data(pkt, AV_PKT_DATA_PALETTE, &size);
 
             if (!palette) {
                 av_log(s, AV_LOG_ERROR, "PAL8 packet is missing palette in extradata\n");
                 return AVERROR_INVALIDDATA;
             }
             if (size != AVPALETTE_SIZE) {
                 av_log(s, AV_LOG_ERROR, "Invalid palette extradata\n");
                 return AVERROR_INVALIDDATA;
             }
             gif_image_write_header(s->pb, video_enc, gif->loop, palette);
         }
 

         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,

 };