/
IMG_gif.c
800 lines (686 loc) · 22.8 KB
1
/*
2
SDL_image: An example image loading library for use with SDL
3
Copyright (C) 1997-2020 Sam Lantinga <slouken@libsdl.org>
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
This software is provided 'as-is', without any express or implied
warranty. In no event will the authors be held liable for any damages
arising from the use of this software.
Permission is granted to anyone to use this software for any purpose,
including commercial applications, and to alter it and redistribute it
freely, subject to the following restrictions:
1. The origin of this software must not be misrepresented; you must not
claim that you wrote the original software. If you use this software
in a product, an acknowledgment in the product documentation would be
appreciated but is not required.
2. Altered source versions must be plainly marked as such, and must not be
misrepresented as being the original software.
3. This notice may not be removed or altered from any source distribution.
20
21
22
23
24
25
26
27
28
29
*/
/* This is a GIF image file loading framework */
#include "SDL_image.h"
#ifdef LOAD_GIF
/* Code from here to end of file has been adapted from XPaint: */
/* +-------------------------------------------------------------------+ */
30
31
/* | Copyright 1990, 1991, 1993 David Koblas. | */
/* | Copyright 1996 Torsten Martinsen. | */
32
33
34
35
36
/* | Permission to use, copy, modify, and distribute this software | */
/* | and its documentation for any purpose and without fee is hereby | */
/* | granted, provided that the above copyright notice appear in all | */
/* | copies and that both that copyright notice and this permission | */
/* | notice appear in supporting documentation. This software is | */
37
/* | provided "as is" without express or implied warranty. | */
38
39
40
41
42
43
44
45
46
47
48
/* +-------------------------------------------------------------------+ */
/* Adapted for use in SDL by Sam Lantinga -- 7/20/98 */
/* Changes to work with SDL:
Include SDL header file
Use SDL_Surface rather than xpaint Image structure
Define SDL versions of RWSetMsg(), ImageNewCmap() and ImageSetCmap()
*/
#include "SDL.h"
49
50
51
#define Image SDL_Surface
#define RWSetMsg IMG_SetError
#define ImageNewCmap(w, h, s) SDL_CreateRGBSurface(SDL_SWSURFACE,w,h,8,0,0,0,0)
52
#define ImageSetCmap(s, i, R, G, B) do { \
53
54
55
56
s->format->palette->colors[i].r = R; \
s->format->palette->colors[i].g = G; \
s->format->palette->colors[i].b = B; \
} while (0)
57
58
/* * * * * */
59
60
61
62
#define GIF_DISPOSE_NA 0 /* No disposal specified */
#define GIF_DISPOSE_NONE 1 /* Do not dispose */
#define GIF_DISPOSE_RESTORE_BACKGROUND 2 /* Restore to background */
#define GIF_DISPOSE_RESTORE_PREVIOUS 3 /* Restore to previous */
63
64
#define MAXCOLORMAPSIZE 256
65
66
67
#define TRUE 1
#define FALSE 0
68
69
70
71
#define CM_RED 0
#define CM_GREEN 1
#define CM_BLUE 2
72
73
#define MAX_LWZ_BITS 12
74
75
76
77
#define INTERLACE 0x40
#define LOCALCOLORMAP 0x80
#define BitSet(byte, bit) (((byte) & (bit)) == (bit))
78
79
#define ReadOK(file,buffer,len) SDL_RWread(file, buffer, len, 1)
80
81
#define LM_to_uint(a,b) (((b)<<8)|(a))
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
typedef struct {
struct {
unsigned int Width;
unsigned int Height;
unsigned char ColorMap[3][MAXCOLORMAPSIZE];
unsigned int BitPixel;
unsigned int ColorResolution;
unsigned int Background;
unsigned int AspectRatio;
int GrayScale;
} GifScreen;
struct {
int transparent;
int delayTime;
int inputFlag;
int disposal;
} Gif89;
unsigned char buf[280];
int curbit, lastbit, done, last_byte;
int fresh;
int code_size, set_code_size;
int max_code, max_code_size;
int firstcode, oldcode;
int clear_code, end_code;
int table[2][(1 << MAX_LWZ_BITS)];
int stack[(1 << (MAX_LWZ_BITS)) * 2], *sp;
int ZeroDataBlock;
} State_t;
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
typedef struct
{
Image *image;
int x, y;
int disposal;
int delay;
} Frame_t;
typedef struct
{
int count;
Frame_t *frames;
} Anim_t;
130
static int ReadColorMap(SDL_RWops * src, int number,
131
unsigned char buffer[3][MAXCOLORMAPSIZE], int *flag);
132
133
134
135
static int DoExtension(SDL_RWops * src, int label, State_t * state);
static int GetDataBlock(SDL_RWops * src, unsigned char *buf, State_t * state);
static int GetCode(SDL_RWops * src, int code_size, int flag, State_t * state);
static int LWZReadByte(SDL_RWops * src, int flag, int input_code_size, State_t * state);
136
static Image *ReadImage(SDL_RWops * src, int len, int height, int,
137
unsigned char cmap[3][MAXCOLORMAPSIZE],
138
int gray, int interlace, int ignore, State_t * state);
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
static SDL_bool NormalizeFrames(Frame_t *frames, int count)
{
SDL_Surface *image;
int i;
int lastDispose = GIF_DISPOSE_RESTORE_BACKGROUND;
int iRestore = 0;
Uint32 fill;
SDL_Rect rect;
if (SDL_HasColorKey(frames[0].image)) {
image = SDL_ConvertSurfaceFormat(frames[0].image, SDL_PIXELFORMAT_ARGB8888, 0);
} else {
image = SDL_ConvertSurfaceFormat(frames[0].image, SDL_PIXELFORMAT_RGB888, 0);
}
if (!image) {
return SDL_FALSE;
}
fill = SDL_MapRGBA(image->format, 0, 0, 0, SDL_ALPHA_TRANSPARENT);
rect.x = 0;
rect.y = 0;
rect.w = image->w;
rect.h = image->h;
for (i = 0; i < count; ++i) {
switch (lastDispose) {
case GIF_DISPOSE_RESTORE_BACKGROUND:
SDL_FillRect(image, &rect, fill);
break;
case GIF_DISPOSE_RESTORE_PREVIOUS:
SDL_BlitSurface(frames[iRestore].image, &rect, image, &rect);
break;
default:
break;
}
if (frames[i].disposal != GIF_DISPOSE_RESTORE_PREVIOUS) {
iRestore = i;
}
rect.x = (Sint16)frames[i].x;
rect.y = (Sint16)frames[i].y;
rect.w = frames[i].image->w;
rect.h = frames[i].image->h;
SDL_BlitSurface(frames[i].image, NULL, image, &rect);
SDL_FreeSurface(frames[i].image);
frames[i].image = SDL_DuplicateSurface(image);
190
191
192
if (!frames[i].image) {
return SDL_FALSE;
}
193
194
195
196
197
198
199
200
201
202
203
lastDispose = frames[i].disposal;
}
SDL_FreeSurface( image );
return SDL_TRUE;
}
Anim_t *
IMG_LoadGIF_RW_Internal(SDL_RWops *src, SDL_bool load_anim)
204
205
206
207
208
209
210
211
212
{
unsigned char buf[16];
unsigned char c;
unsigned char localColorMap[3][MAXCOLORMAPSIZE];
int grayScale;
int useGlobalColormap;
int bitPixel;
char version[4];
Image *image = NULL;
213
214
Anim_t *anim;
Frame_t *frames, *frame;
215
State_t state;
216
217
218
state.ZeroDataBlock = FALSE;
state.fresh = FALSE;
219
state.last_byte = 0;
220
221
222
if (src == NULL) {
return NULL;
223
}
224
225
226
227
228
229
230
anim = (Anim_t *)SDL_calloc(1, sizeof(*anim));
if (!anim) {
SDL_OutOfMemory();
return NULL;
}
231
if (!ReadOK(src, buf, 6)) {
232
RWSetMsg("error reading magic number");
233
234
goto done;
}
235
if (SDL_strncmp((char *) buf, "GIF", 3) != 0) {
236
RWSetMsg("not a GIF file");
237
238
goto done;
}
239
SDL_memcpy(version, (char *) buf + 3, 3);
240
241
version[3] = '\0';
242
if ((SDL_strcmp(version, "87a") != 0) && (SDL_strcmp(version, "89a") != 0)) {
243
RWSetMsg("bad version number, not '87a' or '89a'");
244
245
goto done;
}
246
247
248
state.Gif89.transparent = -1;
state.Gif89.delayTime = -1;
state.Gif89.inputFlag = -1;
249
state.Gif89.disposal = GIF_DISPOSE_NA;
250
251
if (!ReadOK(src, buf, 7)) {
252
RWSetMsg("failed to read screen descriptor");
253
254
goto done;
}
255
256
257
258
259
260
state.GifScreen.Width = LM_to_uint(buf[0], buf[1]);
state.GifScreen.Height = LM_to_uint(buf[2], buf[3]);
state.GifScreen.BitPixel = 2 << (buf[4] & 0x07);
state.GifScreen.ColorResolution = (((buf[4] & 0x70) >> 3) + 1);
state.GifScreen.Background = buf[5];
state.GifScreen.AspectRatio = buf[6];
261
262
if (BitSet(buf[4], LOCALCOLORMAP)) { /* Global Colormap */
263
264
265
if (ReadColorMap(src, state.GifScreen.BitPixel,
state.GifScreen.ColorMap, &state.GifScreen.GrayScale)) {
RWSetMsg("error reading global colormap");
266
goto done;
267
}
268
}
269
for ( ; ; ) {
270
271
if (!ReadOK(src, &c, 1)) {
RWSetMsg("EOF / read error on image data");
272
goto done;
273
274
}
if (c == ';') { /* GIF terminator */
275
goto done;
276
}
277
278
279
if (c == '!') { /* Extension */
if (!ReadOK(src, &c, 1)) {
RWSetMsg("EOF / read error on extention function code");
280
goto done;
281
282
283
}
DoExtension(src, c, &state);
continue;
284
}
285
286
287
if (c != ',') { /* Not a valid start character */
continue;
}
288
289
290
if (!ReadOK(src, buf, 9)) {
RWSetMsg("couldn't read left/top/width/height");
291
goto done;
292
293
}
useGlobalColormap = !BitSet(buf[8], LOCALCOLORMAP);
294
295
bitPixel = 1 << ((buf[8] & 0x07) + 1);
296
297
298
299
if (!useGlobalColormap) {
if (ReadColorMap(src, bitPixel, localColorMap, &grayScale)) {
RWSetMsg("error reading local colormap");
300
goto done;
301
302
303
304
305
}
image = ReadImage(src, LM_to_uint(buf[4], buf[5]),
LM_to_uint(buf[6], buf[7]),
bitPixel, localColorMap, grayScale,
BitSet(buf[8], INTERLACE),
306
0, &state);
307
308
309
310
311
} else {
image = ReadImage(src, LM_to_uint(buf[4], buf[5]),
LM_to_uint(buf[6], buf[7]),
state.GifScreen.BitPixel, state.GifScreen.ColorMap,
state.GifScreen.GrayScale, BitSet(buf[8], INTERLACE),
312
0, &state);
313
}
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
if (image) {
if (state.Gif89.transparent >= 0) {
SDL_SetColorKey(image, SDL_TRUE, state.Gif89.transparent);
}
frames = (Frame_t *)SDL_realloc(anim->frames, (anim->count + 1) * sizeof(*anim->frames));
if (!frames) {
SDL_OutOfMemory();
goto done;
}
++anim->count;
anim->frames = frames;
frame = &anim->frames[anim->count - 1];
frame->image = image;
frame->x = LM_to_uint(buf[0], buf[1]);
frame->y = LM_to_uint(buf[2], buf[3]);
frame->disposal = state.Gif89.disposal;
333
334
335
336
337
if (state.Gif89.delayTime < 2) {
frame->delay = 100; /* Default animation delay, matching browsers and Qt */
} else {
frame->delay = state.Gif89.delayTime * 10;
}
338
339
340
341
342
343
if (!load_anim) {
/* We only need one frame, we're done */
goto done;
}
}
344
345
346
}
done:
347
348
349
350
351
352
353
354
355
if (anim->count > 1) {
/* Normalize the frames */
if (!NormalizeFrames(anim->frames, anim->count)) {
int i;
for (i = 0; i < anim->count; ++i) {
SDL_FreeSurface(anim->frames[i].image);
}
anim->count = 0;
}
356
}
357
358
359
360
361
362
if (anim->count == 0) {
SDL_free(anim->frames);
SDL_free(anim);
return NULL;
}
return anim;
363
364
365
366
367
368
369
370
371
372
373
374
375
}
static int
ReadColorMap(SDL_RWops *src, int number,
unsigned char buffer[3][MAXCOLORMAPSIZE], int *gray)
{
int i;
unsigned char rgb[3];
int flag;
flag = TRUE;
for (i = 0; i < number; ++i) {
376
377
378
379
380
381
382
383
if (!ReadOK(src, rgb, sizeof(rgb))) {
RWSetMsg("bad colormap");
return 1;
}
buffer[CM_RED][i] = rgb[0];
buffer[CM_GREEN][i] = rgb[1];
buffer[CM_BLUE][i] = rgb[2];
flag &= (rgb[0] == rgb[1] && rgb[1] == rgb[2]);
384
385
386
387
}
#if 0
if (flag)
388
*gray = (number == 2) ? PBM_TYPE : PGM_TYPE;
389
else
390
*gray = PPM_TYPE;
391
392
393
394
395
396
397
398
#else
*gray = 0;
#endif
return FALSE;
}
static int
399
DoExtension(SDL_RWops *src, int label, State_t * state)
400
{
401
unsigned char buf[256];
402
403
switch (label) {
404
case 0x01: /* Plain Text Extension */
405
break;
406
case 0xff: /* Application Extension */
407
break;
408
case 0xfe: /* Comment Extension */
409
while (GetDataBlock(src, buf, state) > 0)
410
411
;
return FALSE;
412
case 0xf9: /* Graphic Control Extension */
413
(void) GetDataBlock(src, buf, state);
414
415
416
417
418
419
state->Gif89.disposal = (buf[0] >> 2) & 0x7;
state->Gif89.inputFlag = (buf[0] >> 1) & 0x1;
state->Gif89.delayTime = LM_to_uint(buf[1], buf[2]);
if ((buf[0] & 0x1) != 0)
state->Gif89.transparent = buf[3];
420
while (GetDataBlock(src, buf, state) > 0)
421
422
;
return FALSE;
423
default:
424
break;
425
426
}
427
while (GetDataBlock(src, buf, state) > 0)
428
;
429
430
431
432
433
return FALSE;
}
static int
434
GetDataBlock(SDL_RWops *src, unsigned char *buf, State_t * state)
435
436
437
438
{
unsigned char count;
if (!ReadOK(src, &count, 1)) {
439
440
/* pm_message("error in getting DataBlock size" ); */
return -1;
441
}
442
state->ZeroDataBlock = count == 0;
443
444
if ((count != 0) && (!ReadOK(src, buf, count))) {
445
446
/* pm_message("error in reading DataBlock" ); */
return -1;
447
448
449
450
451
}
return count;
}
static int
452
GetCode(SDL_RWops *src, int code_size, int flag, State_t * state)
453
454
455
456
457
{
int i, j, ret;
unsigned char count;
if (flag) {
458
459
460
461
state->curbit = 0;
state->lastbit = 0;
state->done = FALSE;
return 0;
462
}
463
if ((state->curbit + code_size) >= state->lastbit) {
464
465
466
467
468
469
470
if (state->done) {
if (state->curbit >= state->lastbit)
RWSetMsg("ran off the end of my bits");
return -1;
}
state->buf[0] = state->buf[state->last_byte - 2];
state->buf[1] = state->buf[state->last_byte - 1];
471
472
473
474
475
if ((ret = GetDataBlock(src, &state->buf[2], state)) > 0)
count = (unsigned char) ret;
else {
count = 0;
476
state->done = TRUE;
477
}
478
479
480
481
state->last_byte = 2 + count;
state->curbit = (state->curbit - state->lastbit) + 16;
state->lastbit = (2 + count) * 8;
482
483
}
ret = 0;
484
for (i = state->curbit, j = 0; j < code_size; ++i, ++j)
485
ret |= ((state->buf[i / 8] & (1 << (i % 8))) != 0) << j;
486
487
state->curbit += code_size;
488
489
490
491
492
return ret;
}
static int
493
LWZReadByte(SDL_RWops *src, int flag, int input_code_size, State_t * state)
494
495
496
497
{
int code, incode;
register int i;
498
499
500
501
/* Fixed buffer overflow found by Michael Skladnikiewicz */
if (input_code_size > MAX_LWZ_BITS)
return -1;
502
if (flag) {
503
504
505
506
507
508
state->set_code_size = input_code_size;
state->code_size = state->set_code_size + 1;
state->clear_code = 1 << state->set_code_size;
state->end_code = state->clear_code + 1;
state->max_code_size = 2 * state->clear_code;
state->max_code = state->clear_code + 2;
509
510
GetCode(src, 0, TRUE, state);
511
512
state->fresh = TRUE;
513
514
515
516
517
518
519
520
for (i = 0; i < state->clear_code; ++i) {
state->table[0][i] = 0;
state->table[1][i] = i;
}
state->table[1][0] = 0;
for (; i < (1 << MAX_LWZ_BITS); ++i)
state->table[0][i] = 0;
521
522
state->sp = state->stack;
523
524
return 0;
525
} else if (state->fresh) {
526
527
528
529
530
state->fresh = FALSE;
do {
state->firstcode = state->oldcode = GetCode(src, state->code_size, FALSE, state);
} while (state->firstcode == state->clear_code);
return state->firstcode;
531
532
}
if (state->sp > state->stack)
533
return *--state->sp;
534
535
while ((code = GetCode(src, state->code_size, FALSE, state)) >= 0) {
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
if (code == state->clear_code) {
for (i = 0; i < state->clear_code; ++i) {
state->table[0][i] = 0;
state->table[1][i] = i;
}
for (; i < (1 << MAX_LWZ_BITS); ++i)
state->table[0][i] = state->table[1][i] = 0;
state->code_size = state->set_code_size + 1;
state->max_code_size = 2 * state->clear_code;
state->max_code = state->clear_code + 2;
state->sp = state->stack;
state->firstcode = state->oldcode = GetCode(src, state->code_size, FALSE, state);
return state->firstcode;
} else if (code == state->end_code) {
int count;
unsigned char buf[260];
if (state->ZeroDataBlock)
return -2;
while ((count = GetDataBlock(src, buf, state)) > 0)
;
if (count != 0) {
/*
* pm_message("missing EOD in data stream (common occurence)");
*/
}
return -2;
565
}
566
incode = code;
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
if (code >= state->max_code) {
*state->sp++ = state->firstcode;
code = state->oldcode;
}
while (code >= state->clear_code) {
/* Guard against buffer overruns */
if (code < 0 || code >= (1 << MAX_LWZ_BITS)) {
RWSetMsg("invalid LWZ data");
return -3;
}
*state->sp++ = state->table[1][code];
if (code == state->table[0][code]) {
RWSetMsg("circular table entry BIG ERROR");
return -3;
}
code = state->table[0][code];
584
585
586
587
588
}
/* Guard against buffer overruns */
if (code < 0 || code >= (1 << MAX_LWZ_BITS)) {
RWSetMsg("invalid LWZ data");
589
return -4;
590
}
591
592
593
594
595
596
597
598
599
600
601
*state->sp++ = state->firstcode = state->table[1][code];
if ((code = state->max_code) < (1 << MAX_LWZ_BITS)) {
state->table[0][code] = state->oldcode;
state->table[1][code] = state->firstcode;
++state->max_code;
if ((state->max_code >= state->max_code_size) &&
(state->max_code_size < (1 << MAX_LWZ_BITS))) {
state->max_code_size *= 2;
++state->code_size;
}
602
}
603
state->oldcode = incode;
604
605
606
if (state->sp > state->stack)
return *--state->sp;
607
608
609
610
611
612
}
return code;
}
static Image *
ReadImage(SDL_RWops * src, int len, int height, int cmapSize,
613
unsigned char cmap[3][MAXCOLORMAPSIZE],
614
int gray, int interlace, int ignore, State_t * state)
615
616
617
618
619
620
{
Image *image;
unsigned char c;
int i, v;
int xpos = 0, ypos = 0, pass = 0;
621
622
(void) gray; /* unused */
623
/*
624
** Initialize the compression routines
625
626
*/
if (!ReadOK(src, &c, 1)) {
627
628
RWSetMsg("EOF / read error on image data");
return NULL;
629
}
630
if (LWZReadByte(src, TRUE, c, state) < 0) {
631
632
RWSetMsg("error reading image");
return NULL;
633
634
}
/*
635
** If this is an "uninteresting picture" ignore it.
636
637
*/
if (ignore) {
638
639
640
while (LWZReadByte(src, FALSE, c, state) >= 0)
;
return NULL;
641
642
643
644
}
image = ImageNewCmap(len, height, cmapSize);
for (i = 0; i < cmapSize; i++)
645
646
ImageSetCmap(image, i, cmap[CM_RED][i],
cmap[CM_GREEN][i], cmap[CM_BLUE][i]);
647
648
while ((v = LWZReadByte(src, FALSE, c, state)) >= 0) {
649
((Uint8 *)image->pixels)[xpos + ypos * image->pitch] = (Uint8)v;
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
++xpos;
if (xpos == len) {
xpos = 0;
if (interlace) {
switch (pass) {
case 0:
case 1:
ypos += 8;
break;
case 2:
ypos += 4;
break;
case 3:
ypos += 2;
break;
}
if (ypos >= height) {
++pass;
switch (pass) {
case 1:
ypos = 4;
break;
case 2:
ypos = 2;
break;
case 3:
ypos = 1;
break;
default:
goto fini;
}
}
} else {
++ypos;
685
686
}
}
687
688
if (ypos >= height)
break;
689
690
691
692
693
694
695
}
fini:
return image;
}
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
770
771
772
773
774
775
776
777
778
779
780
/* Load a GIF type animation from an SDL datasource */
IMG_Animation *IMG_LoadGIFAnimation_RW(SDL_RWops *src)
{
Anim_t *internal = IMG_LoadGIF_RW_Internal(src, SDL_TRUE);
if (internal) {
IMG_Animation *anim = (IMG_Animation *)SDL_malloc(sizeof(*anim));
if (anim) {
anim->w = internal->frames[0].image->w;
anim->h = internal->frames[0].image->h;
anim->count = internal->count;
anim->frames = (SDL_Surface **)SDL_calloc(anim->count, sizeof(*anim->frames));
anim->delays = (int *)SDL_calloc(anim->count, sizeof(*anim->delays));
if (anim->frames && anim->delays) {
int i;
for (i = 0; i < anim->count; ++i) {
anim->frames[i] = internal->frames[i].image;
anim->delays[i] = internal->frames[i].delay;
}
} else {
IMG_FreeAnimation(anim);
anim = NULL;
}
}
if (!anim) {
SDL_OutOfMemory();
}
SDL_free(internal->frames);
SDL_free(internal);
return anim;
}
return NULL;
}
#else
/* Load a GIF type animation from an SDL datasource */
IMG_Animation *IMG_LoadGIFAnimation_RW(SDL_RWops *src)
{
return NULL;
}
#endif /* LOAD_GIF */
#if !defined(__APPLE__) || defined(SDL_IMAGE_USE_COMMON_BACKEND)
#ifdef LOAD_GIF
/* See if an image is contained in a data source */
int IMG_isGIF(SDL_RWops *src)
{
Sint64 start;
int is_GIF;
char magic[6];
if ( !src )
return 0;
start = SDL_RWtell(src);
is_GIF = 0;
if ( SDL_RWread(src, magic, sizeof(magic), 1) ) {
if ( (SDL_strncmp(magic, "GIF", 3) == 0) &&
((SDL_memcmp(magic + 3, "87a", 3) == 0) ||
(SDL_memcmp(magic + 3, "89a", 3) == 0)) ) {
is_GIF = 1;
}
}
SDL_RWseek(src, start, RW_SEEK_SET);
return(is_GIF);
}
/* Load a GIF type image from an SDL datasource */
SDL_Surface *IMG_LoadGIF_RW(SDL_RWops *src)
{
SDL_Surface *image = NULL;
Anim_t *internal = IMG_LoadGIF_RW_Internal(src, SDL_FALSE);
if (internal) {
image = internal->frames[0].image;
SDL_free(internal->frames);
SDL_free(internal);
}
return image;
}
781
#else
782
783
784
#if _MSC_VER >= 1300
#pragma warning(disable : 4100) /* warning C4100: 'op' : unreferenced formal parameter */
#endif
785
786
787
788
/* See if an image is contained in a data source */
int IMG_isGIF(SDL_RWops *src)
{
789
return(0);
790
791
792
793
794
}
/* Load a GIF type image from an SDL datasource */
SDL_Surface *IMG_LoadGIF_RW(SDL_RWops *src)
{
795
return(NULL);
796
797
798
}
#endif /* LOAD_GIF */
799
800
#endif /* !defined(__APPLE__) || defined(SDL_IMAGE_USE_COMMON_BACKEND) */