libavformat/gifdec.c

   1 /*
   2  * GIF decoder
   3  * Copyright (c) 2003 Fabrice Bellard.
   4  *
   5  * This library is free software; you can redistribute it and/or
   6  * modify it under the terms of the GNU Lesser General Public
   7  * License as published by the Free Software Foundation; either
   8  * version 2 of the License, or (at your option) any later version.
   9  *
  10  * This library is distributed in the hope that it will be useful,
  11  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * Lesser General Public License for more details.
  14  *
  15  * You should have received a copy of the GNU Lesser General Public
  16  * License along with this library; if not, write to the Free Software
  17  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  18  */
  19 #include "avformat.h"
  20
  21 int gif_write(ByteIOContext *pb, AVImageInfo *info);
  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 int gif_image_probe(AVProbeData * pd)
 146 {
 147     if (pd->buf_size >= 24 &&
 148         (memcmp(pd->buf, gif87a_sig, 6) == 0 ||
 149          memcmp(pd->buf, gif89a_sig, 6) == 0))
 150         return AVPROBE_SCORE_MAX - 1;
 151     else
 152         return 0;
 153 }
 154
 155
 156 static void GLZWDecodeInit(GifState * s, int csize)
 157 {
 158     /* read buffer */
 159     s->eob_reached = 0;
 160     s->pbuf = s->buf;
 161     s->ebuf = s->buf;
 162     s->bbuf = 0;
 163     s->bbits = 0;
 164
 165     /* decoder */
 166     s->codesize = csize;
 167     s->cursize = s->codesize + 1;
 168     s->curmask = mask[s->cursize];
 169     s->top_slot = 1 << s->cursize;
 170     s->clear_code = 1 << s->codesize;
 171     s->end_code = s->clear_code + 1;
 172     s->slot = s->newcodes = s->clear_code + 2;
 173     s->oc = s->fc = 0;
 174     s->sp = s->stack;
 175 }
 176
 177 /* XXX: optimize */
 178 static inline int GetCode(GifState * s)
 179 {
 180     int c, sizbuf;
 181     uint8_t *ptr;
 182
 183     while (s->bbits < s->cursize) {
 184         ptr = s->pbuf;
 185         if (ptr >= s->ebuf) {
 186             if (!s->eob_reached) {
 187                 sizbuf = get_byte(s->f);
 188                 s->ebuf = s->buf + sizbuf;
 189                 s->pbuf = s->buf;
 190                 if (sizbuf > 0) {
 191                     get_buffer(s->f, s->buf, sizbuf);
 192                 } else {
 193                     s->eob_reached = 1;
 194                 }
 195             }
 196             ptr = s->pbuf;
 197         }
 198         s->bbuf |= ptr[0] << s->bbits;
 199         ptr++;
 200         s->pbuf = ptr;
 201         s->bbits += 8;
 202     }
 203     c = s->bbuf & s->curmask;
 204     s->bbuf >>= s->cursize;
 205     s->bbits -= s->cursize;
 206     return c;
 207 }
 208
 209 /* NOTE: the algorithm here is inspired from the LZW GIF decoder
 210    written by Steven A. Bennett in 1987. */
 211 /* return the number of byte decoded */
 212 static int GLZWDecode(GifState * s, uint8_t * buf, int len)
 213 {
 214     int l, c, code, oc, fc;
 215     uint8_t *sp;
 216
 217     if (s->end_code < 0)
 218         return 0;
 219
 220     l = len;
 221     sp = s->sp;
 222     oc = s->oc;
 223     fc = s->fc;
 224
 225     while (sp > s->stack) {
 226         *buf++ = *(--sp);
 227         if ((--l) == 0)
 228             goto the_end;
 229     }
 230
 231     for (;;) {
 232         c = GetCode(s);
 233         if (c == s->end_code) {
 234             s->end_code = -1;
 235             break;
 236         } else if (c == s->clear_code) {
 237             s->cursize = s->codesize + 1;
 238             s->curmask = mask[s->cursize];
 239             s->slot = s->newcodes;
 240             s->top_slot = 1 << s->cursize;
 241             while ((c = GetCode(s)) == s->clear_code);
 242             if (c == s->end_code) {
 243                 s->end_code = -1;
 244                 break;
 245             }
 246             /* test error */
 247             if (c >= s->slot)
 248                 c = 0;
 249             fc = oc = c;
 250             *buf++ = c;
 251             if ((--l) == 0)
 252                 break;
 253         } else {
 254             code = c;
 255             if (code >= s->slot) {
 256                 *sp++ = fc;
 257                 code = oc;
 258             }
 259             while (code >= s->newcodes) {
 260                 *sp++ = s->suffix[code];
 261                 code = s->prefix[code];
 262             }
 263             *sp++ = code;
 264             if (s->slot < s->top_slot) {
 265                 s->suffix[s->slot] = fc = code;
 266                 s->prefix[s->slot++] = oc;
 267                 oc = c;
 268             }
 269             if (s->slot >= s->top_slot) {
 270                 if (s->cursize < MAXBITS) {
 271                     s->top_slot <<= 1;
 272                     s->curmask = mask[++s->cursize];
 273                 }
 274             }
 275             while (sp > s->stack) {
 276                 *buf++ = *(--sp);
 277                 if ((--l) == 0)
 278                     goto the_end;
 279             }
 280         }
 281     }
 282   the_end:
 283     s->sp = sp;
 284     s->oc = oc;
 285     s->fc = fc;
 286     return len - l;
 287 }
 288
 289 static int gif_read_image(GifState *s)
 290 {
 291     ByteIOContext *f = s->f;
 292     int left, top, width, height, bits_per_pixel, code_size, flags;
 293     int is_interleaved, has_local_palette, y, x, pass, y1, linesize, n, i;
 294     uint8_t *ptr, *line, *d, *spal, *palette, *sptr, *ptr1;
 295
 296     left = get_le16(f);
 297     top = get_le16(f);
 298     width = get_le16(f);
 299     height = get_le16(f);
 300     flags = get_byte(f);
 301     is_interleaved = flags & 0x40;
 302     has_local_palette = flags & 0x80;
 303     bits_per_pixel = (flags & 0x07) + 1;
 304 #ifdef DEBUG
 305     printf("gif: image x=%d y=%d w=%d h=%d\n", left, top, width, height);
 306 #endif
 307
 308     if (has_local_palette) {
 309         get_buffer(f, s->local_palette, 3 * (1 << bits_per_pixel));
 310         palette = s->local_palette;
 311     } else {
 312         palette = s->global_palette;
 313         bits_per_pixel = s->bits_per_pixel;
 314     }
 315
 316     /* verify that all the image is inside the screen dimensions */
 317     if (left + width > s->screen_width ||
 318         top + height > s->screen_height)
 319         return -EINVAL;
 320
 321     /* build the palette */
 322     if (s->pix_fmt == PIX_FMT_RGB24) {
 323         line = av_malloc(width);
 324         if (!line)
 325             return -ENOMEM;
 326     } else {
 327         n = (1 << bits_per_pixel);
 328         spal = palette;
 329         for(i = 0; i < n; i++) {
 330             s->image_palette[i] = (0xff << 24) |
 331                 (spal[0] << 16) | (spal[1] << 8) | (spal[2]);
 332             spal += 3;
 333         }
 334         for(; i < 256; i++)
 335             s->image_palette[i] = (0xff << 24);
 336         /* handle transparency */
 337         if (s->transparent_color_index >= 0)
 338             s->image_palette[s->transparent_color_index] = 0;
 339         line = NULL;
 340     }
 341
 342     /* now get the image data */
 343     s->f = f;
 344     code_size = get_byte(f);
 345     GLZWDecodeInit(s, code_size);
 346
 347     /* read all the image */
 348     linesize = s->image_linesize;
 349     ptr1 = s->image_buf + top * linesize + (left * 3);
 350     ptr = ptr1;
 351     pass = 0;
 352     y1 = 0;
 353     for (y = 0; y < height; y++) {
 354         if (s->pix_fmt == PIX_FMT_RGB24) {
 355             /* transcode to RGB24 */
 356             GLZWDecode(s, line, width);
 357             d = ptr;
 358             sptr = line;
 359             for(x = 0; x < width; x++) {
 360                 spal = palette + sptr[0] * 3;
 361                 d[0] = spal[0];
 362                 d[1] = spal[1];
 363                 d[2] = spal[2];
 364                 d += 3;
 365                 sptr++;
 366             }
 367         } else {
 368             GLZWDecode(s, ptr, width);
 369         }
 370         if (is_interleaved) {
 371             switch(pass) {
 372             default:
 373             case 0:
 374             case 1:
 375                 y1 += 8;
 376                 ptr += linesize * 8;
 377                 if (y1 >= height) {
 378                     y1 = 4;
 379                     if (pass == 0)
 380                         ptr = ptr1 + linesize * 4;
 381                     else
 382                         ptr = ptr1 + linesize * 2;
 383                     pass++;
 384                 }
 385                 break;
 386             case 2:
 387                 y1 += 4;
 388                 ptr += linesize * 4;
 389                 if (y1 >= height) {
 390                     y1 = 1;
 391                     ptr = ptr1 + linesize;
 392                     pass++;
 393                 }
 394                 break;
 395             case 3:
 396                 y1 += 2;
 397                 ptr += linesize * 2;
 398                 break;
 399             }
 400         } else {
 401             ptr += linesize;
 402         }
 403     }
 404     av_free(line);
 405
 406     /* read the garbage data until end marker is found */
 407     while (!s->eob_reached)
 408         GetCode(s);
 409     return 0;
 410 }
 411
 412 static int gif_read_extension(GifState *s)
 413 {
 414     ByteIOContext *f = s->f;
 415     int ext_code, ext_len, i, gce_flags, gce_transparent_index;
 416
 417     /* extension */
 418     ext_code = get_byte(f);
 419     ext_len = get_byte(f);
 420 #ifdef DEBUG
 421     printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
 422 #endif
 423     switch(ext_code) {
 424     case 0xf9:
 425         if (ext_len != 4)
 426             goto discard_ext;
 427         s->transparent_color_index = -1;
 428         gce_flags = get_byte(f);
 429         s->gce_delay = get_le16(f);
 430         gce_transparent_index = get_byte(f);
 431         if (gce_flags & 0x01)
 432             s->transparent_color_index = gce_transparent_index;
 433         else
 434             s->transparent_color_index = -1;
 435         s->gce_disposal = (gce_flags >> 2) & 0x7;
 436 #ifdef DEBUG
 437         printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
 438                gce_flags, s->gce_delay,
 439                s->transparent_color_index, s->gce_disposal);
 440 #endif
 441         ext_len = get_byte(f);
 442         break;
 443     }
 444
 445     /* NOTE: many extension blocks can come after */
 446  discard_ext:
 447     while (ext_len != 0) {
 448         for (i = 0; i < ext_len; i++)
 449             get_byte(f);
 450         ext_len = get_byte(f);
 451 #ifdef DEBUG
 452         printf("gif: ext_len1=%d\n", ext_len);
 453 #endif
 454     }
 455     return 0;
 456 }
 457
 458 static int gif_read_header1(GifState *s)
 459 {
 460     ByteIOContext *f = s->f;
 461     uint8_t sig[6];
 462     int ret, v, n;
 463     int has_global_palette;
 464
 465     /* read gif signature */
 466     ret = get_buffer(f, sig, 6);
 467     if (ret != 6)
 468         return -1;
 469     if (memcmp(sig, gif87a_sig, 6) != 0 &&
 470         memcmp(sig, gif89a_sig, 6) != 0)
 471         return -1;
 472
 473     /* read screen header */
 474     s->transparent_color_index = -1;
 475     s->screen_width = get_le16(f);
 476     s->screen_height = get_le16(f);
 477     if(   (unsigned)s->screen_width  > 32767
 478        || (unsigned)s->screen_height > 32767){
 479         av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
 480         return -1;
 481     }
 482
 483     v = get_byte(f);
 484     s->color_resolution = ((v & 0x70) >> 4) + 1;
 485     has_global_palette = (v & 0x80);
 486     s->bits_per_pixel = (v & 0x07) + 1;
 487     s->background_color_index = get_byte(f);
 488     get_byte(f);                /* ignored */
 489 #ifdef DEBUG
 490     printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
 491            s->screen_width, s->screen_height, s->bits_per_pixel,
 492            has_global_palette);
 493 #endif
 494     if (has_global_palette) {
 495         n = 1 << s->bits_per_pixel;
 496         get_buffer(f, s->global_palette, n * 3);
 497     }
 498     return 0;
 499 }
 500
 501 static int gif_parse_next_image(GifState *s)
 502 {
 503     ByteIOContext *f = s->f;
 504     int ret, code;
 505
 506     for (;;) {
 507         code = url_fgetc(f);
 508 #ifdef DEBUG
 509         printf("gif: code=%02x '%c'\n", code, code);
 510 #endif
 511         switch (code) {
 512         case ',':
 513             if (gif_read_image(s) < 0)
 514                 return AVERROR_IO;
 515             ret = 0;
 516             goto the_end;
 517         case ';':
 518             /* end of image */
 519             ret = AVERROR_IO;
 520             goto the_end;
 521         case '!':
 522             if (gif_read_extension(s) < 0)
 523                 return AVERROR_IO;
 524             break;
 525         case EOF:
 526         default:
 527             /* error or errneous EOF */
 528             ret = AVERROR_IO;
 529             goto the_end;
 530         }
 531     }
 532   the_end:
 533     return ret;
 534 }
 535
 536 static int gif_read_header(AVFormatContext * s1,
 537                            AVFormatParameters * ap)
 538 {
 539     GifState *s = s1->priv_data;
 540     ByteIOContext *f = &s1->pb;
 541     AVStream *st;
 542
 543     s->f = f;
 544     if (gif_read_header1(s) < 0)
 545         return -1;
 546
 547     /* allocate image buffer */
 548     s->image_linesize = s->screen_width * 3;
 549     s->image_buf = av_malloc(s->screen_height * s->image_linesize);
 550     if (!s->image_buf)
 551         return -ENOMEM;
 552     s->pix_fmt = PIX_FMT_RGB24;
 553     /* now we are ready: build format streams */
 554     st = av_new_stream(s1, 0);
 555     if (!st)
 556         return -1;
 557
 558     st->codec->codec_type = CODEC_TYPE_VIDEO;
 559     st->codec->codec_id = CODEC_ID_RAWVIDEO;
 560     st->codec->time_base.den = 5;
 561     st->codec->time_base.num = 1;
 562     /* XXX: check if screen size is always valid */
 563     st->codec->width = s->screen_width;
 564     st->codec->height = s->screen_height;
 565     st->codec->pix_fmt = PIX_FMT_RGB24;
 566     return 0;
 567 }
 568
 569 static int gif_read_packet(AVFormatContext * s1,
 570                            AVPacket * pkt)
 571 {
 572     GifState *s = s1->priv_data;
 573     int ret;
 574
 575     ret = gif_parse_next_image(s);
 576     if (ret < 0)
 577         return ret;
 578
 579     /* XXX: avoid copying */
 580     if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {
 581         return AVERROR_IO;
 582     }
 583     pkt->stream_index = 0;
 584     memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);
 585     return 0;
 586 }
 587
 588 static int gif_read_close(AVFormatContext *s1)
 589 {
 590     GifState *s = s1->priv_data;
 591     av_free(s->image_buf);
 592     return 0;
 593 }
 594
 595 /* read gif as image */
 596 static int gif_read(ByteIOContext *f,
 597                     int (*alloc_cb)(void *opaque, AVImageInfo *info), void *opaque)
 598 {
 599     GifState s1, *s = &s1;
 600     AVImageInfo info1, *info = &info1;
 601     int ret;
 602
 603     memset(s, 0, sizeof(GifState));
 604     s->f = f;
 605     if (gif_read_header1(s) < 0)
 606         return -1;
 607     info->width = s->screen_width;
 608     info->height = s->screen_height;
 609     info->pix_fmt = PIX_FMT_PAL8;
 610     ret = alloc_cb(opaque, info);
 611     if (ret)
 612         return ret;
 613     s->image_buf = info->pict.data[0];
 614     s->image_linesize = info->pict.linesize[0];
 615     s->image_palette = (uint32_t *)info->pict.data[1];
 616
 617     if (gif_parse_next_image(s) < 0)
 618         return -1;
 619     return 0;
 620 }
 621
 622 AVInputFormat gif_demuxer =
 623 {
 624     "gif",
 625     "gif format",
 626     sizeof(GifState),
 627     gif_video_probe,
 628     gif_read_header,
 629     gif_read_packet,
 630     gif_read_close,
 631 };
 632
 633 AVImageFormat gif_image_format = {
 634     "gif",
 635     "gif",
 636     gif_image_probe,
 637     gif_read,
 638     (1 << PIX_FMT_PAL8),
 639 #ifdef CONFIG_GIF_MUXER
 640     gif_write,
 641 #endif
 642 };