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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., 59 Temple Place, Suite 330, Boston, MA  02111-1307  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_iformat =
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
    gif_write,
640
};