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ffmpeg / libavformat / gifdec.c @ 1d7d9935

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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 -EINVAL;
309

    
310
    /* build the palette */
311
    if (s->pix_fmt == PIX_FMT_RGB24) {
312
        line = av_malloc(width);
313
        if (!line)
314
            return -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 = 4;
368
                    if (pass == 0)
369
                        ptr = ptr1 + linesize * 4;
370
                    else
371
                        ptr = ptr1 + linesize * 2;
372
                    pass++;
373
                }
374
                break;
375
            case 2:
376
                y1 += 4;
377
                ptr += linesize * 4;
378
                if (y1 >= height) {
379
                    y1 = 1;
380
                    ptr = ptr1 + linesize;
381
                    pass++;
382
                }
383
                break;
384
            case 3:
385
                y1 += 2;
386
                ptr += linesize * 2;
387
                break;
388
            }
389
        } else {
390
            ptr += linesize;
391
        }
392
    }
393
    av_free(line);
394

    
395
    /* read the garbage data until end marker is found */
396
    while (!s->eob_reached)
397
        GetCode(s);
398
    return 0;
399
}
400

    
401
static int gif_read_extension(GifState *s)
402
{
403
    ByteIOContext *f = s->f;
404
    int ext_code, ext_len, i, gce_flags, gce_transparent_index;
405

    
406
    /* extension */
407
    ext_code = get_byte(f);
408
    ext_len = get_byte(f);
409
#ifdef DEBUG
410
    printf("gif: ext_code=0x%x len=%d\n", ext_code, ext_len);
411
#endif
412
    switch(ext_code) {
413
    case 0xf9:
414
        if (ext_len != 4)
415
            goto discard_ext;
416
        s->transparent_color_index = -1;
417
        gce_flags = get_byte(f);
418
        s->gce_delay = get_le16(f);
419
        gce_transparent_index = get_byte(f);
420
        if (gce_flags & 0x01)
421
            s->transparent_color_index = gce_transparent_index;
422
        else
423
            s->transparent_color_index = -1;
424
        s->gce_disposal = (gce_flags >> 2) & 0x7;
425
#ifdef DEBUG
426
        printf("gif: gce_flags=%x delay=%d tcolor=%d disposal=%d\n",
427
               gce_flags, s->gce_delay,
428
               s->transparent_color_index, s->gce_disposal);
429
#endif
430
        ext_len = get_byte(f);
431
        break;
432
    }
433

    
434
    /* NOTE: many extension blocks can come after */
435
 discard_ext:
436
    while (ext_len != 0) {
437
        for (i = 0; i < ext_len; i++)
438
            get_byte(f);
439
        ext_len = get_byte(f);
440
#ifdef DEBUG
441
        printf("gif: ext_len1=%d\n", ext_len);
442
#endif
443
    }
444
    return 0;
445
}
446

    
447
static int gif_read_header1(GifState *s)
448
{
449
    ByteIOContext *f = s->f;
450
    uint8_t sig[6];
451
    int ret, v, n;
452
    int has_global_palette;
453

    
454
    /* read gif signature */
455
    ret = get_buffer(f, sig, 6);
456
    if (ret != 6)
457
        return -1;
458
    if (memcmp(sig, gif87a_sig, 6) != 0 &&
459
        memcmp(sig, gif89a_sig, 6) != 0)
460
        return -1;
461

    
462
    /* read screen header */
463
    s->transparent_color_index = -1;
464
    s->screen_width = get_le16(f);
465
    s->screen_height = get_le16(f);
466
    if(   (unsigned)s->screen_width  > 32767
467
       || (unsigned)s->screen_height > 32767){
468
        av_log(NULL, AV_LOG_ERROR, "picture size too large\n");
469
        return -1;
470
    }
471

    
472
    v = get_byte(f);
473
    s->color_resolution = ((v & 0x70) >> 4) + 1;
474
    has_global_palette = (v & 0x80);
475
    s->bits_per_pixel = (v & 0x07) + 1;
476
    s->background_color_index = get_byte(f);
477
    get_byte(f);                /* ignored */
478
#ifdef DEBUG
479
    printf("gif: screen_w=%d screen_h=%d bpp=%d global_palette=%d\n",
480
           s->screen_width, s->screen_height, s->bits_per_pixel,
481
           has_global_palette);
482
#endif
483
    if (has_global_palette) {
484
        n = 1 << s->bits_per_pixel;
485
        get_buffer(f, s->global_palette, n * 3);
486
    }
487
    return 0;
488
}
489

    
490
static int gif_parse_next_image(GifState *s)
491
{
492
    ByteIOContext *f = s->f;
493
    int ret, code;
494

    
495
    for (;;) {
496
        code = url_fgetc(f);
497
#ifdef DEBUG
498
        printf("gif: code=%02x '%c'\n", code, code);
499
#endif
500
        switch (code) {
501
        case ',':
502
            if (gif_read_image(s) < 0)
503
                return AVERROR_IO;
504
            ret = 0;
505
            goto the_end;
506
        case ';':
507
            /* end of image */
508
            ret = AVERROR_IO;
509
            goto the_end;
510
        case '!':
511
            if (gif_read_extension(s) < 0)
512
                return AVERROR_IO;
513
            break;
514
        case EOF:
515
        default:
516
            /* error or errneous EOF */
517
            ret = AVERROR_IO;
518
            goto the_end;
519
        }
520
    }
521
  the_end:
522
    return ret;
523
}
524

    
525
static int gif_read_header(AVFormatContext * s1,
526
                           AVFormatParameters * ap)
527
{
528
    GifState *s = s1->priv_data;
529
    ByteIOContext *f = &s1->pb;
530
    AVStream *st;
531

    
532
    s->f = f;
533
    if (gif_read_header1(s) < 0)
534
        return -1;
535

    
536
    /* allocate image buffer */
537
    s->image_linesize = s->screen_width * 3;
538
    s->image_buf = av_malloc(s->screen_height * s->image_linesize);
539
    if (!s->image_buf)
540
        return -ENOMEM;
541
    s->pix_fmt = PIX_FMT_RGB24;
542
    /* now we are ready: build format streams */
543
    st = av_new_stream(s1, 0);
544
    if (!st)
545
        return -1;
546

    
547
    st->codec->codec_type = CODEC_TYPE_VIDEO;
548
    st->codec->codec_id = CODEC_ID_RAWVIDEO;
549
    st->codec->time_base.den = 5;
550
    st->codec->time_base.num = 1;
551
    /* XXX: check if screen size is always valid */
552
    st->codec->width = s->screen_width;
553
    st->codec->height = s->screen_height;
554
    st->codec->pix_fmt = PIX_FMT_RGB24;
555
    return 0;
556
}
557

    
558
static int gif_read_packet(AVFormatContext * s1,
559
                           AVPacket * pkt)
560
{
561
    GifState *s = s1->priv_data;
562
    int ret;
563

    
564
    ret = gif_parse_next_image(s);
565
    if (ret < 0)
566
        return ret;
567

    
568
    /* XXX: avoid copying */
569
    if (av_new_packet(pkt, s->screen_width * s->screen_height * 3)) {
570
        return AVERROR_IO;
571
    }
572
    pkt->stream_index = 0;
573
    memcpy(pkt->data, s->image_buf, s->screen_width * s->screen_height * 3);
574
    return 0;
575
}
576

    
577
static int gif_read_close(AVFormatContext *s1)
578
{
579
    GifState *s = s1->priv_data;
580
    av_free(s->image_buf);
581
    return 0;
582
}
583

    
584
AVInputFormat gif_demuxer =
585
{
586
    "gif",
587
    "gif format",
588
    sizeof(GifState),
589
    gif_video_probe,
590
    gif_read_header,
591
    gif_read_packet,
592
    gif_read_close,
593
};