libavformat/gif.c

   1 /*
   2  * Animated GIF muxer
   3  * Copyright (c) 2000 Fabrice Bellard.
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /*
  23  * First version by Francois Revol revol@free.fr
  24  *
  25  * Features and limitations:
  26  * - currently no compression is performed,
  27  *   in fact the size of the data is 9/8 the size of the image in 8bpp
  28  * - uses only a global standard palette
  29  * - tested with IE 5.0, Opera for BeOS, NetPositive (BeOS), and Mozilla (BeOS).
  30  *
  31  * Reference documents:
  32  * http://www.goice.co.jp/member/mo/formats/gif.html
  33  * http://astronomy.swin.edu.au/pbourke/dataformats/gif/
  34  * http://www.dcs.ed.ac.uk/home/mxr/gfx/2d/GIF89a.txt
  35  *
  36  * this url claims to have an LZW algorithm not covered by Unisys patent:
  37  * http://www.msg.net/utility/whirlgif/gifencod.html
  38  * could help reduce the size of the files _a lot_...
  39  * some sites mentions an RLE type compression also.
  40  */
  41
  42 #include "avformat.h"
  43 #include "libavcodec/bitstream.h"
  44
  45 /* bitstream minipacket size */
  46 #define GIF_CHUNKS 100
  47
  48 /* slows down the decoding (and some browsers don't like it) */
  49 /* update on the 'some browsers don't like it issue from above: this was probably due to missing 'Data Sub-block Terminator' (byte 19) in the app_header */
  50 #define GIF_ADD_APP_HEADER // required to enable looping of animated gif
  51
  52 typedef struct {
  53     unsigned char r;
  54     unsigned char g;
  55     unsigned char b;
  56 } rgb_triplet;
  57
  58 /* we use the standard 216 color palette */
  59
  60 /* this script was used to create the palette:
  61  * for r in 00 33 66 99 cc ff; do for g in 00 33 66 99 cc ff; do echo -n "    "; for b in 00 33 66 99 cc ff; do
  62  *   echo -n "{ 0x$r, 0x$g, 0x$b }, "; done; echo ""; done; done
  63  */
  64
  65 static const rgb_triplet gif_clut[216] = {
  66     { 0x00, 0x00, 0x00 }, { 0x00, 0x00, 0x33 }, { 0x00, 0x00, 0x66 }, { 0x00, 0x00, 0x99 }, { 0x00, 0x00, 0xcc }, { 0x00, 0x00, 0xff },
  67     { 0x00, 0x33, 0x00 }, { 0x00, 0x33, 0x33 }, { 0x00, 0x33, 0x66 }, { 0x00, 0x33, 0x99 }, { 0x00, 0x33, 0xcc }, { 0x00, 0x33, 0xff },
  68     { 0x00, 0x66, 0x00 }, { 0x00, 0x66, 0x33 }, { 0x00, 0x66, 0x66 }, { 0x00, 0x66, 0x99 }, { 0x00, 0x66, 0xcc }, { 0x00, 0x66, 0xff },
  69     { 0x00, 0x99, 0x00 }, { 0x00, 0x99, 0x33 }, { 0x00, 0x99, 0x66 }, { 0x00, 0x99, 0x99 }, { 0x00, 0x99, 0xcc }, { 0x00, 0x99, 0xff },
  70     { 0x00, 0xcc, 0x00 }, { 0x00, 0xcc, 0x33 }, { 0x00, 0xcc, 0x66 }, { 0x00, 0xcc, 0x99 }, { 0x00, 0xcc, 0xcc }, { 0x00, 0xcc, 0xff },
  71     { 0x00, 0xff, 0x00 }, { 0x00, 0xff, 0x33 }, { 0x00, 0xff, 0x66 }, { 0x00, 0xff, 0x99 }, { 0x00, 0xff, 0xcc }, { 0x00, 0xff, 0xff },
  72     { 0x33, 0x00, 0x00 }, { 0x33, 0x00, 0x33 }, { 0x33, 0x00, 0x66 }, { 0x33, 0x00, 0x99 }, { 0x33, 0x00, 0xcc }, { 0x33, 0x00, 0xff },
  73     { 0x33, 0x33, 0x00 }, { 0x33, 0x33, 0x33 }, { 0x33, 0x33, 0x66 }, { 0x33, 0x33, 0x99 }, { 0x33, 0x33, 0xcc }, { 0x33, 0x33, 0xff },
  74     { 0x33, 0x66, 0x00 }, { 0x33, 0x66, 0x33 }, { 0x33, 0x66, 0x66 }, { 0x33, 0x66, 0x99 }, { 0x33, 0x66, 0xcc }, { 0x33, 0x66, 0xff },
  75     { 0x33, 0x99, 0x00 }, { 0x33, 0x99, 0x33 }, { 0x33, 0x99, 0x66 }, { 0x33, 0x99, 0x99 }, { 0x33, 0x99, 0xcc }, { 0x33, 0x99, 0xff },
  76     { 0x33, 0xcc, 0x00 }, { 0x33, 0xcc, 0x33 }, { 0x33, 0xcc, 0x66 }, { 0x33, 0xcc, 0x99 }, { 0x33, 0xcc, 0xcc }, { 0x33, 0xcc, 0xff },
  77     { 0x33, 0xff, 0x00 }, { 0x33, 0xff, 0x33 }, { 0x33, 0xff, 0x66 }, { 0x33, 0xff, 0x99 }, { 0x33, 0xff, 0xcc }, { 0x33, 0xff, 0xff },
  78     { 0x66, 0x00, 0x00 }, { 0x66, 0x00, 0x33 }, { 0x66, 0x00, 0x66 }, { 0x66, 0x00, 0x99 }, { 0x66, 0x00, 0xcc }, { 0x66, 0x00, 0xff },
  79     { 0x66, 0x33, 0x00 }, { 0x66, 0x33, 0x33 }, { 0x66, 0x33, 0x66 }, { 0x66, 0x33, 0x99 }, { 0x66, 0x33, 0xcc }, { 0x66, 0x33, 0xff },
  80     { 0x66, 0x66, 0x00 }, { 0x66, 0x66, 0x33 }, { 0x66, 0x66, 0x66 }, { 0x66, 0x66, 0x99 }, { 0x66, 0x66, 0xcc }, { 0x66, 0x66, 0xff },
  81     { 0x66, 0x99, 0x00 }, { 0x66, 0x99, 0x33 }, { 0x66, 0x99, 0x66 }, { 0x66, 0x99, 0x99 }, { 0x66, 0x99, 0xcc }, { 0x66, 0x99, 0xff },
  82     { 0x66, 0xcc, 0x00 }, { 0x66, 0xcc, 0x33 }, { 0x66, 0xcc, 0x66 }, { 0x66, 0xcc, 0x99 }, { 0x66, 0xcc, 0xcc }, { 0x66, 0xcc, 0xff },
  83     { 0x66, 0xff, 0x00 }, { 0x66, 0xff, 0x33 }, { 0x66, 0xff, 0x66 }, { 0x66, 0xff, 0x99 }, { 0x66, 0xff, 0xcc }, { 0x66, 0xff, 0xff },
  84     { 0x99, 0x00, 0x00 }, { 0x99, 0x00, 0x33 }, { 0x99, 0x00, 0x66 }, { 0x99, 0x00, 0x99 }, { 0x99, 0x00, 0xcc }, { 0x99, 0x00, 0xff },
  85     { 0x99, 0x33, 0x00 }, { 0x99, 0x33, 0x33 }, { 0x99, 0x33, 0x66 }, { 0x99, 0x33, 0x99 }, { 0x99, 0x33, 0xcc }, { 0x99, 0x33, 0xff },
  86     { 0x99, 0x66, 0x00 }, { 0x99, 0x66, 0x33 }, { 0x99, 0x66, 0x66 }, { 0x99, 0x66, 0x99 }, { 0x99, 0x66, 0xcc }, { 0x99, 0x66, 0xff },
  87     { 0x99, 0x99, 0x00 }, { 0x99, 0x99, 0x33 }, { 0x99, 0x99, 0x66 }, { 0x99, 0x99, 0x99 }, { 0x99, 0x99, 0xcc }, { 0x99, 0x99, 0xff },
  88     { 0x99, 0xcc, 0x00 }, { 0x99, 0xcc, 0x33 }, { 0x99, 0xcc, 0x66 }, { 0x99, 0xcc, 0x99 }, { 0x99, 0xcc, 0xcc }, { 0x99, 0xcc, 0xff },
  89     { 0x99, 0xff, 0x00 }, { 0x99, 0xff, 0x33 }, { 0x99, 0xff, 0x66 }, { 0x99, 0xff, 0x99 }, { 0x99, 0xff, 0xcc }, { 0x99, 0xff, 0xff },
  90     { 0xcc, 0x00, 0x00 }, { 0xcc, 0x00, 0x33 }, { 0xcc, 0x00, 0x66 }, { 0xcc, 0x00, 0x99 }, { 0xcc, 0x00, 0xcc }, { 0xcc, 0x00, 0xff },
  91     { 0xcc, 0x33, 0x00 }, { 0xcc, 0x33, 0x33 }, { 0xcc, 0x33, 0x66 }, { 0xcc, 0x33, 0x99 }, { 0xcc, 0x33, 0xcc }, { 0xcc, 0x33, 0xff },
  92     { 0xcc, 0x66, 0x00 }, { 0xcc, 0x66, 0x33 }, { 0xcc, 0x66, 0x66 }, { 0xcc, 0x66, 0x99 }, { 0xcc, 0x66, 0xcc }, { 0xcc, 0x66, 0xff },
  93     { 0xcc, 0x99, 0x00 }, { 0xcc, 0x99, 0x33 }, { 0xcc, 0x99, 0x66 }, { 0xcc, 0x99, 0x99 }, { 0xcc, 0x99, 0xcc }, { 0xcc, 0x99, 0xff },
  94     { 0xcc, 0xcc, 0x00 }, { 0xcc, 0xcc, 0x33 }, { 0xcc, 0xcc, 0x66 }, { 0xcc, 0xcc, 0x99 }, { 0xcc, 0xcc, 0xcc }, { 0xcc, 0xcc, 0xff },
  95     { 0xcc, 0xff, 0x00 }, { 0xcc, 0xff, 0x33 }, { 0xcc, 0xff, 0x66 }, { 0xcc, 0xff, 0x99 }, { 0xcc, 0xff, 0xcc }, { 0xcc, 0xff, 0xff },
  96     { 0xff, 0x00, 0x00 }, { 0xff, 0x00, 0x33 }, { 0xff, 0x00, 0x66 }, { 0xff, 0x00, 0x99 }, { 0xff, 0x00, 0xcc }, { 0xff, 0x00, 0xff },
  97     { 0xff, 0x33, 0x00 }, { 0xff, 0x33, 0x33 }, { 0xff, 0x33, 0x66 }, { 0xff, 0x33, 0x99 }, { 0xff, 0x33, 0xcc }, { 0xff, 0x33, 0xff },
  98     { 0xff, 0x66, 0x00 }, { 0xff, 0x66, 0x33 }, { 0xff, 0x66, 0x66 }, { 0xff, 0x66, 0x99 }, { 0xff, 0x66, 0xcc }, { 0xff, 0x66, 0xff },
  99     { 0xff, 0x99, 0x00 }, { 0xff, 0x99, 0x33 }, { 0xff, 0x99, 0x66 }, { 0xff, 0x99, 0x99 }, { 0xff, 0x99, 0xcc }, { 0xff, 0x99, 0xff },
 100     { 0xff, 0xcc, 0x00 }, { 0xff, 0xcc, 0x33 }, { 0xff, 0xcc, 0x66 }, { 0xff, 0xcc, 0x99 }, { 0xff, 0xcc, 0xcc }, { 0xff, 0xcc, 0xff },
 101     { 0xff, 0xff, 0x00 }, { 0xff, 0xff, 0x33 }, { 0xff, 0xff, 0x66 }, { 0xff, 0xff, 0x99 }, { 0xff, 0xff, 0xcc }, { 0xff, 0xff, 0xff },
 102 };
 103
 104 /* The GIF format uses reversed order for bitstreams... */
 105 /* at least they don't use PDP_ENDIAN :) */
 106 /* so we 'extend' PutBitContext. hmmm, OOP :) */
 107 /* seems this thing changed slightly since I wrote it... */
 108
 109 #ifdef ALT_BITSTREAM_WRITER
 110 # error no ALT_BITSTREAM_WRITER support for now
 111 #endif
 112
 113 static void gif_put_bits_rev(PutBitContext *s, int n, unsigned int value)
 114 {
 115     unsigned int bit_buf;
 116     int bit_cnt;
 117
 118     //    printf("put_bits=%d %x\n", n, value);
 119     assert(n == 32 || value < (1U << n));
 120
 121     bit_buf = s->bit_buf;
 122     bit_cnt = 32 - s->bit_left; /* XXX:lazyness... was = s->bit_cnt; */
 123
 124     //    printf("n=%d value=%x cnt=%d buf=%x\n", n, value, bit_cnt, bit_buf);
 125     /* XXX: optimize */
 126     if (n < (32-bit_cnt)) {
 127         bit_buf |= value << (bit_cnt);
 128         bit_cnt+=n;
 129     } else {
 130         bit_buf |= value << (bit_cnt);
 131
 132         *s->buf_ptr = bit_buf & 0xff;
 133         s->buf_ptr[1] = (bit_buf >> 8) & 0xff;
 134         s->buf_ptr[2] = (bit_buf >> 16) & 0xff;
 135         s->buf_ptr[3] = (bit_buf >> 24) & 0xff;
 136
 137         //printf("bitbuf = %08x\n", bit_buf);
 138         s->buf_ptr+=4;
 139         if (s->buf_ptr >= s->buf_end)
 140             abort();
 141 //            flush_buffer_rev(s);
 142         bit_cnt=bit_cnt + n - 32;
 143         if (bit_cnt == 0) {
 144             bit_buf = 0;
 145         } else {
 146             bit_buf = value >> (n - bit_cnt);
 147         }
 148     }
 149
 150     s->bit_buf = bit_buf;
 151     s->bit_left = 32 - bit_cnt;
 152 }
 153
 154 /* pad the end of the output stream with zeros */
 155 static void gif_flush_put_bits_rev(PutBitContext *s)
 156 {
 157     while (s->bit_left < 32) {
 158         /* XXX: should test end of buffer */
 159         *s->buf_ptr++=s->bit_buf & 0xff;
 160         s->bit_buf>>=8;
 161         s->bit_left+=8;
 162     }
 163 //    flush_buffer_rev(s);
 164     s->bit_left=32;
 165     s->bit_buf=0;
 166 }
 167
 168 /* !RevPutBitContext */
 169
 170 /* GIF header */
 171 static int gif_image_write_header(ByteIOContext *pb,
 172                                   int width, int height, int loop_count,
 173                                   uint32_t *palette)
 174 {
 175     int i;
 176     unsigned int v;
 177
 178     put_tag(pb, "GIF");
 179     put_tag(pb, "89a");
 180     put_le16(pb, width);
 181     put_le16(pb, height);
 182
 183     put_byte(pb, 0xf7); /* flags: global clut, 256 entries */
 184     put_byte(pb, 0x1f); /* background color index */
 185     put_byte(pb, 0); /* aspect ratio */
 186
 187     /* the global palette */
 188     if (!palette) {
 189         put_buffer(pb, (const unsigned char *)gif_clut, 216*3);
 190         for(i=0;i<((256-216)*3);i++)
 191             put_byte(pb, 0);
 192     } else {
 193         for(i=0;i<256;i++) {
 194             v = palette[i];
 195             put_byte(pb, (v >> 16) & 0xff);
 196             put_byte(pb, (v >> 8) & 0xff);
 197             put_byte(pb, (v) & 0xff);
 198         }
 199     }
 200
 201         /*        update: this is the 'NETSCAPE EXTENSION' that allows for looped animated gif
 202                 see http://members.aol.com/royalef/gifabout.htm#net-extension
 203
 204                 byte   1       : 33 (hex 0x21) GIF Extension code
 205                 byte   2       : 255 (hex 0xFF) Application Extension Label
 206                 byte   3       : 11 (hex (0x0B) Length of Application Block
 207                                          (eleven bytes of data to follow)
 208                 bytes  4 to 11 : "NETSCAPE"
 209                 bytes 12 to 14 : "2.0"
 210                 byte  15       : 3 (hex 0x03) Length of Data Sub-Block
 211                                          (three bytes of data to follow)
 212                 byte  16       : 1 (hex 0x01)
 213                 bytes 17 to 18 : 0 to 65535, an unsigned integer in
 214                                          lo-hi byte format. This indicate the
 215                                          number of iterations the loop should
 216                                          be executed.
 217                 bytes 19       : 0 (hex 0x00) a Data Sub-block Terminator
 218         */
 219
 220     /* application extension header */
 221 #ifdef GIF_ADD_APP_HEADER
 222     if (loop_count >= 0 && loop_count <= 65535) {
 223     put_byte(pb, 0x21);
 224     put_byte(pb, 0xff);
 225     put_byte(pb, 0x0b);
 226         put_tag(pb, "NETSCAPE2.0");  // bytes 4 to 14
 227         put_byte(pb, 0x03); // byte 15
 228         put_byte(pb, 0x01); // byte 16
 229         put_le16(pb, (uint16_t)loop_count);
 230         put_byte(pb, 0x00); // byte 19
 231     }
 232 #endif
 233     return 0;
 234 }
 235
 236 /* this is maybe slow, but allows for extensions */
 237 static inline unsigned char gif_clut_index(uint8_t r, uint8_t g, uint8_t b)
 238 {
 239     return (((r) / 47) % 6) * 6 * 6 + (((g) / 47) % 6) * 6 + (((b) / 47) % 6);
 240 }
 241
 242
 243 static int gif_image_write_image(ByteIOContext *pb,
 244                                  int x1, int y1, int width, int height,
 245                                  const uint8_t *buf, int linesize, int pix_fmt)
 246 {
 247     PutBitContext p;
 248     uint8_t buffer[200]; /* 100 * 9 / 8 = 113 */
 249     int i, left, w, v;
 250     const uint8_t *ptr;
 251     /* image block */
 252
 253     put_byte(pb, 0x2c);
 254     put_le16(pb, x1);
 255     put_le16(pb, y1);
 256     put_le16(pb, width);
 257     put_le16(pb, height);
 258     put_byte(pb, 0x00); /* flags */
 259     /* no local clut */
 260
 261     put_byte(pb, 0x08);
 262
 263     left= width * height;
 264
 265     init_put_bits(&p, buffer, 130);
 266
 267 /*
 268  * the thing here is the bitstream is written as little packets, with a size byte before
 269  * but it's still the same bitstream between packets (no flush !)
 270  */
 271     ptr = buf;
 272     w = width;
 273     while(left>0) {
 274
 275         gif_put_bits_rev(&p, 9, 0x0100); /* clear code */
 276
 277         for(i=(left<GIF_CHUNKS)?left:GIF_CHUNKS;i;i--) {
 278             if (pix_fmt == PIX_FMT_RGB24) {
 279                 v = gif_clut_index(ptr[0], ptr[1], ptr[2]);
 280                 ptr+=3;
 281             } else {
 282                 v = *ptr++;
 283             }
 284             gif_put_bits_rev(&p, 9, v);
 285             if (--w == 0) {
 286                 w = width;
 287                 buf += linesize;
 288                 ptr = buf;
 289             }
 290         }
 291
 292         if(left<=GIF_CHUNKS) {
 293             gif_put_bits_rev(&p, 9, 0x101); /* end of stream */
 294             gif_flush_put_bits_rev(&p);
 295         }
 296         if(pbBufPtr(&p) - p.buf > 0) {
 297             put_byte(pb, pbBufPtr(&p) - p.buf); /* byte count of the packet */
 298             put_buffer(pb, p.buf, pbBufPtr(&p) - p.buf); /* the actual buffer */
 299             p.buf_ptr = p.buf; /* dequeue the bytes off the bitstream */
 300         }
 301         left-=GIF_CHUNKS;
 302     }
 303     put_byte(pb, 0x00); /* end of image block */
 304
 305     return 0;
 306 }
 307
 308 typedef struct {
 309     int64_t time, file_time;
 310     uint8_t buffer[100]; /* data chunks */
 311 } GIFContext;
 312
 313 static int gif_write_header(AVFormatContext *s)
 314 {
 315     GIFContext *gif = s->priv_data;
 316     ByteIOContext *pb = s->pb;
 317     AVCodecContext *enc, *video_enc;
 318     int i, width, height, loop_count /*, rate*/;
 319
 320 /* XXX: do we reject audio streams or just ignore them ?
 321     if(s->nb_streams > 1)
 322         return -1;
 323 */
 324     gif->time = 0;
 325     gif->file_time = 0;
 326
 327     video_enc = NULL;
 328     for(i=0;i<s->nb_streams;i++) {
 329         enc = s->streams[i]->codec;
 330         if (enc->codec_type != CODEC_TYPE_AUDIO)
 331             video_enc = enc;
 332     }
 333
 334     if (!video_enc) {
 335         av_free(gif);
 336         return -1;
 337     } else {
 338         width = video_enc->width;
 339         height = video_enc->height;
 340         loop_count = s->loop_output;
 341 //        rate = video_enc->time_base.den;
 342     }
 343
 344     if (video_enc->pix_fmt != PIX_FMT_RGB24) {
 345         av_log(s, AV_LOG_ERROR, "ERROR: gif only handles the rgb24 pixel format. Use -pix_fmt rgb24.\n");
 346         return AVERROR(EIO);
 347     }
 348
 349     gif_image_write_header(pb, width, height, loop_count, NULL);
 350
 351     put_flush_packet(s->pb);
 352     return 0;
 353 }
 354
 355 static int gif_write_video(AVFormatContext *s,
 356                            AVCodecContext *enc, const uint8_t *buf, int size)
 357 {
 358     ByteIOContext *pb = s->pb;
 359     GIFContext *gif = s->priv_data;
 360     int jiffies;
 361     int64_t delay;
 362
 363     /* graphic control extension block */
 364     put_byte(pb, 0x21);
 365     put_byte(pb, 0xf9);
 366     put_byte(pb, 0x04); /* block size */
 367     put_byte(pb, 0x04); /* flags */
 368
 369     /* 1 jiffy is 1/70 s */
 370     /* the delay_time field indicates the number of jiffies - 1 */
 371     delay = gif->file_time - gif->time;
 372
 373     /* XXX: should use delay, in order to be more accurate */
 374     /* instead of using the same rounded value each time */
 375     /* XXX: don't even remember if I really use it for now */
 376     jiffies = (70*enc->time_base.num/enc->time_base.den) - 1;
 377
 378     put_le16(pb, jiffies);
 379
 380     put_byte(pb, 0x1f); /* transparent color index */
 381     put_byte(pb, 0x00);
 382
 383     gif_image_write_image(pb, 0, 0, enc->width, enc->height,
 384                           buf, enc->width * 3, PIX_FMT_RGB24);
 385
 386     put_flush_packet(s->pb);
 387     return 0;
 388 }
 389
 390 static int gif_write_packet(AVFormatContext *s, AVPacket *pkt)
 391 {
 392     AVCodecContext *codec = s->streams[pkt->stream_index]->codec;
 393     if (codec->codec_type == CODEC_TYPE_AUDIO)
 394         return 0; /* just ignore audio */
 395     else
 396         return gif_write_video(s, codec, pkt->data, pkt->size);
 397 }
 398
 399 static int gif_write_trailer(AVFormatContext *s)
 400 {
 401     ByteIOContext *pb = s->pb;
 402
 403     put_byte(pb, 0x3b);
 404     put_flush_packet(s->pb);
 405     return 0;
 406 }
 407
 408 AVOutputFormat gif_muxer = {
 409     "gif",
 410     NULL_IF_CONFIG_SMALL("GIF Animation"),
 411     "image/gif",
 412     "gif",
 413     sizeof(GIFContext),
 414     CODEC_ID_NONE,
 415     CODEC_ID_RAWVIDEO,
 416     gif_write_header,
 417     gif_write_packet,
 418     gif_write_trailer,
 419 };