libavformat/gifdec.c

   1 /*
   2  * GIF demuxer
   3  * Copyright (c) 2003 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 #include "avformat.h"
  22
  23 //#define DEBUG
  24
  25 #define MAXBITS                 12
  26 #define         SIZTABLE        (1<<MAXBITS)
  27
  28 #define GCE_DISPOSAL_NONE       0
  29 #define GCE_DISPOSAL_INPLACE    1
  30 #define GCE_DISPOSAL_BACKGROUND 2
  31 #define GCE_DISPOSAL_RESTORE    3
  32
  33 typedef struct GifState {
  34     int screen_width;
  35     int screen_height;
  36     int bits_per_pixel;
  37     int background_color_index;
  38     int transparent_color_index;
  39     int color_resolution;
  40     uint8_t *image_buf;
  41     int image_linesize;
  42     uint32_t *image_palette;
  43     int pix_fmt;
  44
  45     /* after the frame is displayed, the disposal method is used */
  46     int gce_disposal;
  47     /* delay during which the frame is shown */
  48     int gce_delay;
  49
  50     /* LZW compatible decoder */
  51     ByteIOContext *f;
  52     int eob_reached;
  53     uint8_t *pbuf, *ebuf;
  54     int bbits;
  55     unsigned int bbuf;
  56
  57     int cursize;                /* The current code size */
  58     int curmask;
  59     int codesize;
  60     int clear_code;
  61     int end_code;
  62     int newcodes;               /* First available code */
  63     int top_slot;               /* Highest code for current size */
  64     int slot;                   /* Last read code */
  65     int fc, oc;
  66     uint8_t *sp;
  67     uint8_t stack[SIZTABLE];
  68     uint8_t suffix[SIZTABLE];
  69     uint16_t prefix[SIZTABLE];
  70
  71     /* aux buffers */
  72     uint8_t global_palette[256 * 3];
  73     uint8_t local_palette[256 * 3];
  74     uint8_t buf[256];
  75 } GifState;
  76
  77
  78 static const uint8_t gif87a_sig[6] = "GIF87a";
  79 static const uint8_t gif89a_sig[6] = "GIF89a";
  80
  81 static const uint16_t mask[17] =
  82 {
  83     0x0000, 0x0001, 0x0003, 0x0007,
  84     0x000F, 0x001F, 0x003F, 0x007F,
  85     0x00FF, 0x01FF, 0x03FF, 0x07FF,
  86     0x0FFF, 0x1FFF, 0x3FFF, 0x7FFF, 0xFFFF
  87 };
  88
  89 /* Probe gif video format or gif image format. The current heuristic
  90    supposes the gif87a is always a single image. For gif89a, we
  91    consider it as a video only if a GCE extension is present in the
  92    first kilobyte. */
  93 static int gif_video_probe(AVProbeData * pd)
  94 {
  95     const uint8_t *p, *p_end;
  96     int bits_per_pixel, has_global_palette, ext_code, ext_len;
  97     int gce_flags, gce_disposal;
  98
  99     if (pd->buf_size < 24 ||
 100         memcmp(pd->buf, gif89a_sig, 6) != 0)
 101         return 0;
 102     p_end = pd->buf + pd->buf_size;
 103     p = pd->buf + 6;
 104     bits_per_pixel = (p[4] & 0x07) + 1;
 105     has_global_palette = (p[4] & 0x80);
 106     p += 7;
 107     if (has_global_palette)
 108         p += (1 << bits_per_pixel) * 3;
 109     for(;;) {
 110         if (p >= p_end)
 111             return 0;
 112         if (*p != '!')
 113             break;
 114         p++;
 115         if (p >= p_end)
 116             return 0;
 117         ext_code = *p++;
 118         if (p >= p_end)
 119             return 0;
 120         ext_len = *p++;
 121         if (ext_code == 0xf9) {
 122             if (p >= p_end)
 123                 return 0;
 124             /* if GCE extension found with gce_disposal != 0: it is
 125                likely to be an animation */
 126             gce_flags = *p++;
 127             gce_disposal = (gce_flags >> 2) & 0x7;
 128             if (gce_disposal != 0)
 129                 return AVPROBE_SCORE_MAX;
 130             else
 131                 return 0;
 132         }
 133         for(;;) {
 134             if (ext_len == 0)
 135                 break;
 136             p += ext_len;
 137             if (p >= p_end)
 138                 return 0;
 139             ext_len = *p++;
 140         }
 141     }
 142     return 0;
 143 }
 144
 145 static void GLZWDecodeInit(GifState * s, int csize)
 146 {
 147     /* read buffer */
 148     s->eob_reached = 0;
 149     s->pbuf = s->buf;
 150     s->ebuf = s->buf;
 151     s->bbuf = 0;
 152     s->bbits = 0;
 153
 154     /* decoder */
 155     s->codesize = csize;
 156     s->cursize = s->codesize + 1;
 157     s->curmask = mask[s->cursize];
 158     s->top_slot = 1 << s->cursize;
 159     s->clear_code = 1 << s->codesize;
 160     s->end_code = s->clear_code + 1;
 161     s->slot = s->newcodes = s->clear_code + 2;
 162     s->oc = s->fc = 0;
 163     s->sp = s->stack;
 164 }
 165
 166 /* XXX: optimize */
 167 static inline int GetCode(GifState * s)
 168 {
 169     int c, sizbuf;
 170     uint8_t *ptr;
 171
 172     while (s->bbits < s->cursize) {
 173         ptr = s->pbuf;
 174         if (ptr >= s->ebuf) {
 175             if (!s->eob_reached) {
 176                 sizbuf = get_byte(s->f);
 177                 s->ebuf = s->buf + sizbuf;
 178                 s->pbuf = s->buf;
 179                 if (sizbuf > 0) {
 180                     get_buffer(s->f, s->buf, sizbuf);
 181                 } else {
 182                     s->eob_reached = 1;
 183                 }
 184             }
 185             ptr = s->pbuf;
 186         }
 187         s->bbuf |= ptr[0] << s->bbits;
 188         ptr++;
 189         s->pbuf = ptr;
 190         s->bbits += 8;
 191     }
 192     c = s->bbuf & s->curmask;
 193     s->bbuf >>= s->cursize;
 194     s->bbits -= s->cursize;
 195     return c;
 196 }
 197
 198 /* NOTE: the algorithm here is inspired from the LZW GIF decoder
 199    written by Steven A. Bennett in 1987. */
 200 /* return the number of byte decoded */
 201 static int GLZWDecode(GifState * s, uint8_t * buf, int len)
 202 {
 203     int l, c, code, oc, fc;
 204     uint8_t *sp;
 205
 206     if (s->end_code < 0)
 207         return 0;
 208
 209     l = len;
 210     sp = s->sp;
 211     oc = s->oc;
 212     fc = s->fc;
 213
 214     while (sp > s->stack) {
 215         *buf++ = *(--sp);
 216         if ((--l) == 0)
 217             goto the_end;
 218     }
 219
 220     for (;;) {
 221         c = GetCode(s);
 222         if (c == s->end_code) {
 223             s->end_code = -1;
 224             break;
 225         } else if (c == s->clear_code) {
 226             s->cursize = s->codesize + 1;
 227             s->curmask = mask[s->cursize];
 228             s->slot = s->newcodes;
 229             s->top_slot = 1 << s->cursize;
 230             while ((c = GetCode(s)) == s->clear_code);
 231             if (c == s->end_code) {
 232                 s->end_code = -1;
 233                 break;
 234             }
 235             /* test error */
 236             if (c >= s->slot)
 237                 c = 0;
 238             fc = oc = c;
 239             *buf++ = c;
 240             if ((--l) == 0)
 241                 break;
 242         } else {
 243             code = c;
 244             if (code >= s->slot) {
 245                 *sp++ = fc;
 246                 code = oc;
 247             }
 248             while (code >= s->newcodes) {
 249                 *sp++ = s->suffix[code];
 250                 code = s->prefix[code];
 251             }
 252             *sp++ = code;
 253             if (s->slot < s->top_slot) {
 254                 s->suffix[s->slot] = fc = code;
 255                 s->prefix[s->slot++] = oc;
 256                 oc = c;
 257             }
 258             if (s->slot >= s->top_slot) {
 259                 if (s->cursize < MAXBITS) {
 260                     s->top_slot <<= 1;
 261                     s->curmask = mask[++s->cursize];
 262                 }
 263             }
 264             while (sp > s->stack) {
 265                 *buf++ = *(--sp);
 266                 if ((--l) == 0)
 267                     goto the_end;
 268             }
 269         }
 270     }
 271   the_end:
 272     s->sp = sp;
 273     s->oc = oc;
 274     s->fc = fc;
 275     return len - l;
 276 }
 277
 278 static int gif_read_image(GifState *s)
 279 {
 280     ByteIOContext *f = s->f;
 281     int left, top, width, height, bits_per_pixel, code_size, flags;
 282     int is_interleaved, has_local_palette, y, x, pass, y1, linesize, n, i;
 283     uint8_t *ptr, *line, *d, *spal, *palette, *sptr, *ptr1;
 284
 285     left = get_le16(f);
 286     top = get_le16(f);
 287     width = get_le16(f);
 288     height = get_le16(f);
 289     flags = get_byte(f);
 290     is_interleaved = flags & 0x40;
 291     has_local_palette = flags & 0x80;
 292     bits_per_pixel = (flags & 0x07) + 1;
 293 #ifdef DEBUG
 294     printf("gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
 295 #endif
 296
 297     if (has_local_palette) {
 298         get_buffer(f, s->local_palette, 3 * (1 << bits_per_pixel));
 299         palette = s->local_palette;
 300     } else {
 301         palette = s->global_palette;
 302         bits_per_pixel = s->bits_per_pixel;
 303     }
 304
 305     /* verify that all the image is inside the screen dimensions */
 306     if (left + width > s->screen_width ||
 307         top + height > s->screen_height)
 308         return AVERROR(EINVAL);
 309
 310     /* build the palette */
 311     if (s->pix_fmt == PIX_FMT_RGB24) {
 312         line = av_malloc(width);
 313         if (!line)
 314             return AVERROR(ENOMEM);
 315     } else {
 316         n = (1 << bits_per_pixel);
 317         spal = palette;
 318         for(i = 0; i < n; i++) {
 319             s->image_palette[i] = (0xff << 24) |
 320                 (spal[0] << 16) | (spal[1] << 8) | (spal[2]);
 321             spal += 3;
 322         }
 323         for(; i < 256; i++)
 324             s->image_palette[i] = (0xff << 24);
 325         /* handle transparency */
 326         if (s->transparent_color_index >= 0)
 327             s->image_palette[s->transparent_color_index] = 0;
 328         line = NULL;
 329     }
 330
 331     /* now get the image data */
 332     s->f = f;
 333     code_size = get_byte(f);
 334     GLZWDecodeInit(s, code_size);
 335
 336     /* read all the image */
 337     linesize = s->image_linesize;
 338     ptr1 = s->image_buf + top * linesize + (left * 3);
 339     ptr = ptr1;
 340     pass = 0;
 341     y1 = 0;
 342     for (y = 0; y < height; y++) {
 343         if (s->pix_fmt == PIX_FMT_RGB24) {
 344             /* transcode to RGB24 */
 345             GLZWDecode(s, line, width);
 346             d = ptr;
 347             sptr = line;
 348             for(x = 0; x < width; x++) {
 349                 spal = palette + sptr[0] * 3;
 350                 d[0] = spal[0];
 351                 d[1] = spal[1];
 352                 d[2] = spal[2];
 353                 d += 3;
 354                 sptr++;
 355             }
 356         } else {
 357             GLZWDecode(s, ptr, width);
 358         }
 359         if (is_interleaved) {
 360             switch(pass) {
 361             default:
 362             case 0:
 363             case 1:
 364                 y1 += 8;
 365                 ptr += linesize * 8;
 366                 if (y1 >= height) {
 367                     y1 = pass == 0 ? 4 : 2;
 368                     ptr = ptr1 + linesize * y1;
 369                     pass++;
 370                 }
 371                 break;
 372             case 2:
 373                 y1 += 4;
 374                 ptr += linesize * 4;
 375                 if (y1 >= height) {
 376                     y1 = 1;
 377                     ptr = ptr1 + linesize;
 378                     pass++;
 379                 }
 380                 break;
 381             case 3:
 382                 y1 += 2;
 383                 ptr += linesize * 2;
 384                 break;
 385             }
 386         } else {
 387             ptr += linesize;
 388         }
 389     }
 390     av_free(line);
 391
 392     /* read the garbage data until end marker is found */
 393     while (!s->eob_reached)
 394         GetCode(s);
 395     return 0;
 396 }
 397
 398 static int gif_read_extension(GifState *s)
 399 {
 400     ByteIOContext *f = s->f;
 401     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
 402
 403     /* extension */
 404     ext_code = get_byte(f);
 405     ext_len = get_byte(f);
 406 #ifdef DEBUG
 407     printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
 408 #endif
 409     switch(ext_code) {
 410     case 0xf9:
 411         if (ext_len != 4)
 412             goto discard_ext;
 413         s->transparent_color_index = -1;
 414         gce_flags = get_byte(f);
 415         s->gce_delay = get_le16(f);
 416         gce_transparent_index = get_byte(f);
 417         if (gce_flags & 0x01)
 418             s->transparent_color_index = gce_transparent_index;
 419         else
 420             s->transparent_color_index = -1;
 421         s->gce_disposal = (gce_flags >> 2) & 0x7;
 422 #ifdef DEBUG
 423         printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
 424                gce_flags, s->gce_delay,
 425                s->transparent_color_index, s->gce_disposal);
 426 #endif
 427         ext_len = get_byte(f);
 428         break;
 429     }
 430
 431     /* NOTE: many extension blocks can come after */
 432  discard_ext:
 433     while (ext_len != 0) {
 434         for (i = 0; i < ext_len; i++)
 435             get_byte(f);
 436         ext_len = get_byte(f);
 437 #ifdef DEBUG
 438         printf("gif: ext_len1=%d\n", ext_len);
 439 #endif
 440     }
 441     return 0;
 442 }
 443
 444 static int gif_read_header1(GifState *s)
 445 {
 446     ByteIOContext *f = s->f;
 447     uint8_t sig[6];
 448     int ret, v, n;
 449     int has_global_palette;
 450
 451     /* read gif signature */
 452     ret = get_buffer(f, sig, 6);
 453     if (ret != 6)
 454         return -1;
 455     if (memcmp(sig, gif87a_sig, 6) != 0 &&
 456         memcmp(sig, gif89a_sig, 6) != 0)
 457         return -1;
 458
 459     /* read screen header */
 460     s->transparent_color_index = -1;
 461     s->screen_width = get_le16(f);
 462     s->screen_height = get_le16(f);
 463     if(   (unsigned)s->screen_width  > 32767
 464        || (unsigned)s->screen_height > 32767){
 465         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
 466         return -1;
 467     }
 468
 469     v = get_byte(f);
 470     s->color_resolution = ((v & 0x70) >> 4) + 1;
 471     has_global_palette = (v & 0x80);
 472     s->bits_per_pixel = (v & 0x07) + 1;
 473     s->background_color_index = get_byte(f);
 474     get_byte(f);                /* ignored */
 475 #ifdef DEBUG
 476     printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
 477            s->screen_width, s->screen_height, s->bits_per_pixel,
 478            has_global_palette);
 479 #endif
 480     if (has_global_palette) {
 481         n = 1 << s->bits_per_pixel;
 482         get_buffer(f, s->global_palette, n * 3);
 483     }
 484     return 0;
 485 }
 486
 487 static int gif_parse_next_image(GifState *s)
 488 {
 489     ByteIOContext *f = s->f;
 490     int ret, code;
 491
 492     for (;;) {
 493         code = url_fgetc(f);
 494 #ifdef DEBUG
 495         printf("gif: code=%02x '%c'\n", code, code);
 496 #endif
 497         switch (code) {
 498         case ',':
 499             if (gif_read_image(s) < 0)
 500                 return AVERROR(EIO);
 501             ret = 0;
 502             goto the_end;
 503         case ';':
 504             /* end of image */
 505             ret = AVERROR(EIO);
 506             goto the_end;
 507         case '!':
 508             if (gif_read_extension(s) < 0)
 509                 return AVERROR(EIO);
 510             break;
 511         case EOF:
 512         default:
 513             /* error or errneous EOF */
 514             ret = AVERROR(EIO);
 515             goto the_end;
 516         }
 517     }
 518   the_end:
 519     return ret;
 520 }
 521
 522 static int gif_read_header(AVFormatContext * s1,
 523                            AVFormatParameters * ap)
 524 {
 525     GifState *s = s1->priv_data;
 526     ByteIOContext *f = s1->pb;
 527     AVStream *st;
 528
 529     s->f = f;
 530     if (gif_read_header1(s) < 0)
 531         return -1;
 532
 533     /* allocate image buffer */
 534     s->image_linesize = s->screen_width * 3;
 535     s->image_buf = av_malloc(s->screen_height * s->image_linesize);
 536     if (!s->image_buf)
 537         return AVERROR(ENOMEM);
 538     s->pix_fmt = PIX_FMT_RGB24;
 539     /* now we are ready: build format streams */
 540     st = av_new_stream(s1, 0);
 541     if (!st)
 542         return -1;
 543
 544     st->codec->codec_type = CODEC_TYPE_VIDEO;
 545     st->codec->codec_id = CODEC_ID_RAWVIDEO;
 546     st->codec->time_base.den = 5;
 547     st->codec->time_base.num = 1;
 548     /* XXX: check if screen size is always valid */
 549     st->codec->width = s->screen_width;
 550     st->codec->height = s->screen_height;
 551     st->codec->pix_fmt = PIX_FMT_RGB24;
 552     return 0;
 553 }
 554
 555 static int gif_read_packet(AVFormatContext * s1,
 556                            AVPacket * pkt)
 557 {
 558     GifState *s = s1->priv_data;
 559     int ret;
 560
 561     ret = gif_parse_next_image(s);
 562     if (ret < 0)
 563         return ret;
 564
 565     /* XXX: avoid copying */
 566     if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {
 567         return AVERROR(EIO);
 568     }
 569     pkt->stream_index = 0;
 570     memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);
 571     return 0;
 572 }
 573
 574 static int gif_read_close(AVFormatContext *s1)
 575 {
 576     GifState *s = s1->priv_data;
 577     av_free(s->image_buf);
 578     return 0;
 579 }
 580
 581 AVInputFormat gif_demuxer =
 582 {
 583     "gif",
 584     "gif format",
 585     sizeof(GifState),
 586     gif_video_probe,
 587     gif_read_header,
 588     gif_read_packet,
 589     gif_read_close,
 590 };