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464122b6 JS |
1 | ///////////////////////////////////////////////////////////////////////////// |
2 | // Name: gifdecod.cpp | |
3 | // Purpose: wxGIFDecoder, GIF reader for wxImage and wxAnimation | |
4 | // Author: Guillermo Rodriguez Garcia <guille@iies.es> | |
9d0e21da GRG |
5 | // Version: 3.04 |
6 | // RCS-ID: $Id$ | |
464122b6 JS |
7 | // Copyright: (c) Guillermo Rodriguez Garcia |
8 | // Licence: wxWindows licence | |
9 | ///////////////////////////////////////////////////////////////////////////// | |
10 | ||
11 | #ifdef __GNUG__ | |
12 | #pragma implementation "gifdecod.h" | |
13 | #endif | |
14 | ||
15 | // For compilers that support precompilation, includes "wx.h". | |
16 | #include "wx/wxprec.h" | |
17 | ||
18 | #ifdef __BORLANDC__ | |
19 | # pragma hdrstop | |
20 | #endif | |
21 | ||
22 | #ifndef WX_PRECOMP | |
7be110e3 | 23 | # include "wx/defs.h" |
464122b6 JS |
24 | #endif |
25 | ||
7be110e3 | 26 | #if wxUSE_STREAMS && wxUSE_GIF |
464122b6 JS |
27 | |
28 | #include <stdlib.h> | |
29 | #include <string.h> | |
464122b6 | 30 | #include "wx/gifdecod.h" |
2ce0a6e2 | 31 | |
464122b6 JS |
32 | |
33 | //--------------------------------------------------------------------------- | |
34 | // wxGIFDecoder constructor and destructor | |
35 | //--------------------------------------------------------------------------- | |
36 | ||
37 | wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim) | |
38 | { | |
9742d3cc | 39 | m_f = s; |
464122b6 JS |
40 | m_anim = anim; |
41 | ||
42 | m_background = -1; | |
43 | m_screenw = 0; | |
44 | m_screenh = 0; | |
45 | ||
46 | m_pimage = NULL; | |
47 | m_pfirst = NULL; | |
48 | m_plast = NULL; | |
49 | m_image = 0; | |
50 | m_nimages = 0; | |
51 | } | |
52 | ||
53 | wxGIFDecoder::~wxGIFDecoder() | |
54 | { | |
55 | Destroy(); | |
56 | } | |
57 | ||
58 | void wxGIFDecoder::Destroy() | |
59 | { | |
e4b8154a | 60 | GIFImage *pimg, *paux; |
464122b6 JS |
61 | |
62 | pimg = m_pfirst; | |
63 | ||
64 | while (pimg != NULL) | |
65 | { | |
66 | paux = pimg->next; | |
67 | free(pimg->p); | |
68 | free(pimg->pal); | |
e4b8154a | 69 | delete pimg; |
464122b6 JS |
70 | pimg = paux; |
71 | } | |
9742d3cc GRG |
72 | |
73 | m_pimage = NULL; | |
74 | m_pfirst = NULL; | |
75 | m_plast = NULL; | |
76 | m_image = 0; | |
77 | m_nimages = 0; | |
464122b6 JS |
78 | } |
79 | ||
80 | ||
81 | //--------------------------------------------------------------------------- | |
82 | // Convert this image to a wxImage object | |
83 | //--------------------------------------------------------------------------- | |
84 | ||
85 | // This function was designed by Vaclav Slavik | |
86 | ||
87 | bool wxGIFDecoder::ConvertToImage(wxImage *image) const | |
88 | { | |
89 | unsigned char *src, *dst, *pal; | |
90 | unsigned long i; | |
91 | int transparent; | |
92 | ||
3c87527e GRG |
93 | /* just in case... */ |
94 | image->Destroy(); | |
95 | ||
464122b6 JS |
96 | /* create the image */ |
97 | image->Create(GetWidth(), GetHeight()); | |
98 | ||
99 | if (!image->Ok()) | |
100 | return FALSE; | |
101 | ||
102 | pal = GetPalette(); | |
103 | src = GetData(); | |
104 | dst = image->GetData(); | |
105 | transparent = GetTransparentColour(); | |
106 | ||
107 | /* set transparent colour mask */ | |
108 | if (transparent != -1) | |
109 | { | |
110 | for (i = 0; i < 256; i++) | |
111 | { | |
112 | if ((pal[3 * i + 0] == 255) && | |
113 | (pal[3 * i + 1] == 0) && | |
114 | (pal[3 * i + 2] == 255)) | |
115 | { | |
116 | pal[3 * i + 2] = 254; | |
117 | } | |
118 | } | |
119 | ||
120 | pal[3 * transparent + 0] = 255, | |
121 | pal[3 * transparent + 1] = 0, | |
122 | pal[3 * transparent + 2] = 255; | |
123 | ||
124 | image->SetMaskColour(255, 0, 255); | |
125 | } | |
126 | else | |
127 | image->SetMask(FALSE); | |
128 | ||
3f4fc796 JS |
129 | // Set the palette |
130 | if (pal) | |
131 | { | |
132 | unsigned char* r = new unsigned char[256]; | |
133 | unsigned char* g = new unsigned char[256]; | |
134 | unsigned char* b = new unsigned char[256]; | |
135 | for (i = 0; i < 256; i++) | |
136 | { | |
137 | r[i] = pal[3*i + 0]; | |
138 | g[i] = pal[3*i + 1]; | |
139 | b[i] = pal[3*i + 2]; | |
140 | } | |
141 | image->SetPalette(wxPalette(256, r, g, b)); | |
142 | delete[] r; delete[] g; delete[] b; | |
143 | } | |
144 | ||
464122b6 JS |
145 | /* copy image data */ |
146 | for (i = 0; i < (GetWidth() * GetHeight()); i++, src++) | |
147 | { | |
148 | *(dst++) = pal[3 * (*src) + 0]; | |
149 | *(dst++) = pal[3 * (*src) + 1]; | |
150 | *(dst++) = pal[3 * (*src) + 2]; | |
151 | } | |
152 | ||
153 | return TRUE; | |
154 | } | |
155 | ||
2ce0a6e2 | 156 | |
464122b6 JS |
157 | //--------------------------------------------------------------------------- |
158 | // Data accessors | |
159 | //--------------------------------------------------------------------------- | |
160 | ||
161 | // Get data for current frame | |
162 | ||
163 | int wxGIFDecoder::GetFrameIndex() const { return m_image; } | |
164 | unsigned char* wxGIFDecoder::GetData() const { return (m_pimage->p); } | |
165 | unsigned char* wxGIFDecoder::GetPalette() const { return (m_pimage->pal); } | |
166 | unsigned int wxGIFDecoder::GetWidth() const { return (m_pimage->w); } | |
167 | unsigned int wxGIFDecoder::GetHeight() const { return (m_pimage->h); } | |
168 | unsigned int wxGIFDecoder::GetTop() const { return (m_pimage->top); } | |
169 | unsigned int wxGIFDecoder::GetLeft() const { return (m_pimage->left); } | |
170 | int wxGIFDecoder::GetTransparentColour() const { return (m_pimage->transparent); } | |
171 | int wxGIFDecoder::GetDisposalMethod() const { return (m_pimage->disposal); } | |
172 | long wxGIFDecoder::GetDelay() const { return (m_pimage->delay); } | |
173 | ||
174 | // Get global data | |
175 | ||
176 | unsigned int wxGIFDecoder::GetLogicalScreenWidth() const { return m_screenw; } | |
177 | unsigned int wxGIFDecoder::GetLogicalScreenHeight() const { return m_screenh; } | |
178 | int wxGIFDecoder::GetBackgroundColour() const { return m_background; } | |
179 | int wxGIFDecoder::GetNumberOfFrames() const { return m_nimages; } | |
180 | bool wxGIFDecoder::IsAnimation() const { return (m_nimages > 1); } | |
181 | ||
182 | ||
183 | //--------------------------------------------------------------------------- | |
184 | // Functions to move through the animation | |
185 | //--------------------------------------------------------------------------- | |
186 | ||
187 | bool wxGIFDecoder::GoFirstFrame() | |
188 | { | |
189 | if (!IsAnimation()) | |
190 | return FALSE; | |
191 | ||
192 | m_image = 1; | |
193 | m_pimage = m_pfirst; | |
194 | return TRUE; | |
195 | } | |
196 | ||
197 | bool wxGIFDecoder::GoLastFrame() | |
198 | { | |
199 | if (!IsAnimation()) | |
200 | return FALSE; | |
201 | ||
202 | m_image = m_nimages; | |
203 | m_pimage = m_plast; | |
204 | return TRUE; | |
205 | } | |
206 | ||
207 | bool wxGIFDecoder::GoNextFrame(bool cyclic) | |
208 | { | |
209 | if (!IsAnimation()) | |
210 | return FALSE; | |
211 | ||
212 | if ((m_image < m_nimages) || (cyclic)) | |
213 | { | |
214 | m_pimage = m_pimage->next; | |
215 | m_image++; | |
216 | ||
217 | if (!m_pimage) | |
218 | { | |
219 | m_image = 1; | |
220 | m_pimage = m_pfirst; | |
221 | } | |
222 | ||
223 | return TRUE; | |
224 | } | |
225 | else | |
226 | return FALSE; | |
2ce0a6e2 | 227 | } |
464122b6 JS |
228 | |
229 | bool wxGIFDecoder::GoPrevFrame(bool cyclic) | |
230 | { | |
231 | if (!IsAnimation()) | |
232 | return FALSE; | |
233 | ||
234 | if ((m_image > 1) || (cyclic)) | |
235 | { | |
236 | m_pimage = m_pimage->prev; | |
237 | m_image--; | |
238 | ||
239 | if (!m_pimage) | |
240 | { | |
241 | m_image = m_nimages; | |
242 | m_pimage = m_plast; | |
243 | } | |
244 | ||
245 | return TRUE; | |
246 | } | |
247 | else | |
248 | return FALSE; | |
249 | } | |
250 | ||
251 | bool wxGIFDecoder::GoFrame(int which) | |
252 | { | |
253 | int i; | |
254 | ||
255 | if (!IsAnimation()) | |
256 | return FALSE; | |
257 | ||
258 | if ((which >= 1) && (which <= m_nimages)) | |
259 | { | |
260 | m_pimage = m_pfirst; | |
261 | ||
262 | for (i = 1; i < which; i++) | |
263 | m_pimage = m_pimage->next; | |
264 | ||
265 | return TRUE; | |
266 | } | |
267 | else | |
268 | return FALSE; | |
269 | } | |
270 | ||
271 | ||
272 | //--------------------------------------------------------------------------- | |
273 | // GIF reading and decoding | |
274 | //--------------------------------------------------------------------------- | |
275 | ||
276 | // getcode: | |
277 | // Reads the next code from the file stream, with size 'bits' | |
278 | // | |
279 | int wxGIFDecoder::getcode(int bits, int ab_fin) | |
280 | { | |
281 | unsigned int mask; /* bit mask */ | |
282 | unsigned int code; /* code (result) */ | |
283 | ||
284 | ||
285 | /* get remaining bits from last byte read */ | |
286 | mask = (1 << bits) - 1; | |
287 | code = (m_lastbyte >> (8 - m_restbits)) & mask; | |
288 | ||
289 | /* keep reading new bytes while needed */ | |
290 | while (bits > m_restbits) | |
291 | { | |
292 | /* if no bytes left in this block, read the next block */ | |
293 | if (m_restbyte == 0) | |
294 | { | |
295 | m_restbyte = (unsigned char)m_f->GetC(); | |
296 | ||
297 | /* Some encoders are a bit broken: instead of issuing | |
298 | * an end-of-image symbol (ab_fin) they come up with | |
299 | * a zero-length subblock!! We catch this here so | |
300 | * that the decoder sees an ab_fin code. | |
301 | */ | |
302 | if (m_restbyte == 0) | |
303 | { | |
304 | code = ab_fin; | |
305 | break; | |
306 | } | |
8708a10f GRG |
307 | |
308 | /* prefetch data */ | |
309 | m_f->Read((void *) m_buffer, m_restbyte); | |
310 | m_bufp = m_buffer; | |
464122b6 JS |
311 | } |
312 | ||
313 | /* read next byte and isolate the bits we need */ | |
8708a10f | 314 | m_lastbyte = (unsigned char) (*m_bufp++); |
464122b6 JS |
315 | mask = (1 << (bits - m_restbits)) - 1; |
316 | code = code + ((m_lastbyte & mask) << m_restbits); | |
317 | m_restbyte--; | |
318 | ||
319 | /* adjust total number of bits extracted from the buffer */ | |
320 | m_restbits = m_restbits + 8; | |
321 | } | |
2ce0a6e2 | 322 | |
464122b6 JS |
323 | /* find number of bits remaining for next code */ |
324 | m_restbits = (m_restbits - bits); | |
325 | ||
326 | return code; | |
327 | } | |
328 | ||
329 | ||
330 | // dgif: | |
331 | // GIF decoding function. The initial code size (aka root size) | |
332 | // is 'bits'. Supports interlaced images (interl == 1). | |
333 | // | |
e4b8154a | 334 | int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits) |
464122b6 JS |
335 | { |
336 | int ab_prefix[4096]; /* alphabet (prefixes) */ | |
337 | int ab_tail[4096]; /* alphabet (tails) */ | |
338 | int stack[4096]; /* decompression stack */ | |
339 | ||
340 | int ab_clr; /* clear code */ | |
341 | int ab_fin; /* end of info code */ | |
342 | int ab_bits; /* actual symbol width, in bits */ | |
343 | int ab_free; /* first free position in alphabet */ | |
344 | int ab_max; /* last possible character in alphabet */ | |
345 | int pass; /* pass number in interlaced images */ | |
346 | int pos; /* index into decompresion stack */ | |
347 | unsigned int x, y; /* position in image buffer */ | |
348 | ||
349 | int code, readcode, lastcode, abcabca; | |
350 | ||
351 | /* these won't change */ | |
352 | ab_clr = (1 << bits); | |
353 | ab_fin = (1 << bits) + 1; | |
354 | ||
355 | /* these will change through the decompression proccess */ | |
356 | ab_bits = bits + 1; | |
357 | ab_free = (1 << bits) + 2; | |
358 | ab_max = (1 << ab_bits) - 1; | |
359 | lastcode = -1; | |
360 | abcabca = -1; | |
361 | pass = 1; | |
362 | pos = x = y = 0; | |
363 | ||
8708a10f | 364 | /* reset decoder vars */ |
464122b6 JS |
365 | m_restbits = 0; |
366 | m_restbyte = 0; | |
367 | m_lastbyte = 0; | |
368 | ||
369 | do | |
370 | { | |
371 | /* get next code */ | |
372 | readcode = code = getcode(ab_bits, ab_fin); | |
373 | ||
374 | /* end of image? */ | |
375 | if (code == ab_fin) break; | |
376 | ||
377 | /* reset alphabet? */ | |
378 | if (code == ab_clr) | |
379 | { | |
380 | /* reset main variables */ | |
381 | ab_bits = bits + 1; | |
382 | ab_free = (1 << bits) + 2; | |
383 | ab_max = (1 << ab_bits) - 1; | |
384 | lastcode = -1; | |
385 | abcabca = -1; | |
386 | ||
387 | /* skip to next code */ | |
388 | continue; | |
389 | } | |
390 | ||
391 | /* unknown code: special case (like in ABCABCA) */ | |
392 | if (code >= ab_free) | |
393 | { | |
394 | code = lastcode; /* take last string */ | |
395 | stack[pos++] = abcabca; /* add first character */ | |
396 | } | |
397 | ||
398 | /* build the string for this code in the stack */ | |
399 | while (code > ab_clr) | |
400 | { | |
401 | stack[pos++] = ab_tail[code]; | |
402 | code = ab_prefix[code]; | |
403 | } | |
404 | stack[pos] = code; /* push last code into the stack */ | |
405 | abcabca = code; /* save for special case */ | |
406 | ||
407 | /* make new entry in alphabet (only if NOT just cleared) */ | |
408 | if (lastcode != -1) | |
409 | { | |
410 | ab_prefix[ab_free] = lastcode; | |
411 | ab_tail[ab_free] = code; | |
412 | ab_free++; | |
413 | ||
414 | if ((ab_free > ab_max) && (ab_bits < 12)) | |
415 | { | |
416 | ab_bits++; | |
417 | ab_max = (1 << ab_bits) - 1; | |
418 | } | |
419 | } | |
420 | ||
421 | /* dump stack data to the buffer */ | |
422 | while (pos >= 0) | |
423 | { | |
424 | (img->p)[x + (y * (img->w))] = (char)stack[pos--]; | |
425 | ||
426 | if (++x >= (img->w)) | |
427 | { | |
428 | x = 0; | |
429 | ||
430 | if (interl) | |
431 | { | |
432 | /* support for interlaced images */ | |
433 | switch (pass) | |
434 | { | |
435 | case 1: y += 8; break; | |
436 | case 2: y += 8; break; | |
437 | case 3: y += 4; break; | |
438 | case 4: y += 2; break; | |
439 | } | |
440 | if (y >= (img->h)) | |
441 | { | |
442 | switch (++pass) | |
443 | { | |
444 | case 2: y = 4; break; | |
445 | case 3: y = 2; break; | |
446 | case 4: y = 1; break; | |
447 | } | |
448 | } | |
449 | } | |
450 | else | |
451 | { | |
452 | /* non-interlaced */ | |
453 | y++; | |
454 | } | |
455 | } | |
456 | } | |
457 | ||
458 | pos = 0; | |
459 | lastcode = readcode; | |
460 | } | |
461 | while (code != ab_fin); | |
462 | ||
463 | return 0; | |
464 | } | |
465 | ||
466 | ||
3c87527e GRG |
467 | // CanRead: |
468 | // Returns TRUE if the file looks like a valid GIF, FALSE otherwise. | |
469 | // | |
470 | bool wxGIFDecoder::CanRead() | |
471 | { | |
472 | unsigned char buf[3]; | |
473 | ||
3c87527e | 474 | m_f->Read(buf, 3); |
700ec454 | 475 | m_f->SeekI(-3, wxFromCurrent); |
3c87527e GRG |
476 | |
477 | return (memcmp(buf, "GIF", 3) == 0); | |
478 | } | |
479 | ||
480 | ||
464122b6 JS |
481 | // ReadGIF: |
482 | // Reads and decodes one or more GIF images, depending on whether | |
483 | // animated GIF support is enabled. Can read GIFs with any bit | |
484 | // size (color depth), but the output images are always expanded | |
485 | // to 8 bits per pixel. Also, the image palettes always contain | |
8141573c | 486 | // 256 colors, although some of them may be unused. Returns wxGIF_OK |
e4b8154a GRG |
487 | // (== 0) on success, or an error code if something fails (see |
488 | // header file for details) | |
464122b6 JS |
489 | // |
490 | int wxGIFDecoder::ReadGIF() | |
491 | { | |
492 | int ncolors, bits, interl, transparent, disposal, i; | |
493 | long size; | |
494 | long delay; | |
495 | unsigned char type; | |
496 | unsigned char pal[768]; | |
497 | unsigned char buf[16]; | |
e4b8154a | 498 | GIFImage **ppimg, *pimg, *pprev; |
464122b6 | 499 | |
3c87527e GRG |
500 | /* check GIF signature */ |
501 | if (!CanRead()) | |
e4b8154a | 502 | return wxGIF_INVFORMAT; |
464122b6 | 503 | |
8141573c | 504 | /* check for animated GIF support (ver. >= 89a) */ |
464122b6 JS |
505 | m_f->Read(buf, 6); |
506 | ||
464122b6 JS |
507 | if (memcmp(buf + 3, "89a", 3) < 0) |
508 | m_anim = FALSE; | |
509 | ||
510 | /* read logical screen descriptor block (LSDB) */ | |
511 | m_f->Read(buf, 7); | |
512 | m_screenw = buf[0] + 256 * buf[1]; | |
513 | m_screenh = buf[2] + 256 * buf[3]; | |
514 | ||
515 | /* load global color map if available */ | |
516 | if ((buf[4] & 0x80) == 0x80) | |
517 | { | |
518 | m_background = buf[5]; | |
519 | ||
520 | ncolors = 2 << (buf[4] & 0x07); | |
521 | m_f->Read(pal, 3 * ncolors); | |
522 | } | |
523 | ||
524 | /* transparent colour, disposal method and delay default to unused */ | |
525 | transparent = -1; | |
526 | disposal = -1; | |
527 | delay = -1; | |
528 | ||
529 | /* read images */ | |
530 | ppimg = &m_pfirst; | |
531 | pprev = NULL; | |
532 | pimg = NULL; | |
533 | ||
8141573c GRG |
534 | bool done = FALSE; |
535 | ||
536 | while(!done) | |
464122b6 JS |
537 | { |
538 | type = (unsigned char)m_f->GetC(); | |
539 | ||
540 | /* end of data? */ | |
541 | if (type == 0x3B) | |
8141573c GRG |
542 | { |
543 | done = TRUE; | |
544 | } | |
545 | else | |
464122b6 JS |
546 | /* extension block? */ |
547 | if (type == 0x21) | |
548 | { | |
549 | if (((unsigned char)m_f->GetC()) == 0xF9) | |
550 | /* graphics control extension, parse it */ | |
551 | { | |
552 | m_f->Read(buf, 6); | |
553 | ||
554 | /* read delay and convert from 1/100 of a second to ms */ | |
555 | delay = 10 * (buf[2] + 256 * buf[3]); | |
556 | ||
557 | /* read transparent colour index, if used */ | |
558 | if (buf[1] & 0x01) | |
559 | transparent = buf[4]; | |
560 | ||
561 | /* read disposal method */ | |
562 | disposal = (buf[1] & 0x1C) - 1; | |
563 | } | |
564 | else | |
565 | /* other extension, skip */ | |
2ce0a6e2 | 566 | { |
464122b6 JS |
567 | while ((i = (unsigned char)m_f->GetC()) != 0) |
568 | { | |
464122b6 JS |
569 | m_f->SeekI(i, wxFromCurrent); |
570 | } | |
571 | } | |
572 | } | |
8141573c | 573 | else |
464122b6 JS |
574 | /* image descriptor block? */ |
575 | if (type == 0x2C) | |
576 | { | |
577 | /* allocate memory for IMAGEN struct */ | |
e4b8154a | 578 | pimg = (*ppimg) = new GIFImage(); |
464122b6 JS |
579 | |
580 | if (pimg == NULL) | |
581 | { | |
582 | Destroy(); | |
e4b8154a | 583 | return wxGIF_MEMERR; |
464122b6 JS |
584 | } |
585 | ||
586 | /* fill in the data */ | |
587 | m_f->Read(buf, 9); | |
588 | pimg->left = buf[4] + 256 * buf[5]; | |
589 | pimg->top = buf[4] + 256 * buf[5]; | |
590 | pimg->w = buf[4] + 256 * buf[5]; | |
591 | pimg->h = buf[6] + 256 * buf[7]; | |
592 | interl = ((buf[8] & 0x40)? 1 : 0); | |
593 | size = pimg->w * pimg->h; | |
594 | ||
595 | pimg->transparent = transparent; | |
596 | pimg->disposal = disposal; | |
597 | pimg->delay = delay; | |
598 | pimg->next = NULL; | |
599 | pimg->prev = pprev; | |
600 | pprev = pimg; | |
601 | ppimg = &pimg->next; | |
602 | ||
603 | /* allocate memory for image and palette */ | |
13111b2a | 604 | pimg->p = (unsigned char *) malloc((size_t)size); |
464122b6 JS |
605 | pimg->pal = (unsigned char *) malloc(768); |
606 | ||
607 | if ((!pimg->p) || (!pimg->pal)) | |
608 | { | |
609 | Destroy(); | |
e4b8154a | 610 | return wxGIF_MEMERR; |
464122b6 JS |
611 | } |
612 | ||
613 | /* load local color map if available, else use global map */ | |
614 | if ((buf[8] & 0x80) == 0x80) | |
615 | { | |
616 | ncolors = 2 << (buf[8] & 0x07); | |
617 | m_f->Read(pimg->pal, 3 * ncolors); | |
618 | } | |
619 | else | |
620 | memcpy(pimg->pal, pal, 768); | |
621 | ||
622 | /* get initial code size from first byte in raster data */ | |
623 | bits = (unsigned char)m_f->GetC(); | |
624 | ||
625 | /* decode image */ | |
626 | dgif(pimg, interl, bits); | |
464122b6 | 627 | m_nimages++; |
464122b6 | 628 | |
8141573c GRG |
629 | /* if this is not an animated GIF, exit after first image */ |
630 | if (!m_anim) | |
631 | done = TRUE; | |
632 | } | |
464122b6 JS |
633 | } |
634 | ||
8141573c | 635 | /* setup image pointers */ |
464122b6 JS |
636 | if (m_nimages != 0) |
637 | { | |
638 | m_image = 1; | |
639 | m_plast = pimg; | |
640 | m_pimage = m_pfirst; | |
641 | } | |
642 | ||
8141573c GRG |
643 | /* try to read to the end of the stream */ |
644 | while (type != 0x3B) | |
645 | { | |
646 | type = (unsigned char)m_f->GetC(); | |
647 | ||
648 | if (type == 0x21) | |
649 | { | |
650 | /* extension type */ | |
651 | (void) m_f->GetC(); | |
652 | ||
653 | /* skip all data */ | |
654 | while ((i = (unsigned char)m_f->GetC()) != 0) | |
655 | { | |
656 | m_f->SeekI(i, wxFromCurrent); | |
657 | } | |
658 | } | |
659 | else if (type == 0x2C) | |
660 | { | |
661 | /* image descriptor block */ | |
662 | m_f->Read(buf, 9); | |
663 | ||
664 | /* local color map */ | |
665 | if ((buf[8] & 0x80) == 0x80) | |
666 | { | |
667 | ncolors = 2 << (buf[8] & 0x07); | |
9742d3cc | 668 | m_f->SeekI(3 * ncolors, wxFromCurrent); |
8141573c GRG |
669 | } |
670 | ||
671 | /* initial code size */ | |
672 | (void) m_f->GetC(); | |
673 | ||
674 | /* skip all data */ | |
675 | while ((i = (unsigned char)m_f->GetC()) != 0) | |
676 | { | |
677 | m_f->SeekI(i, wxFromCurrent); | |
678 | } | |
679 | } | |
9742d3cc | 680 | else if ((type != 0x3B) && (type != 00)) /* testing */ |
8141573c GRG |
681 | { |
682 | /* images are OK, but couldn't read to the end of the stream */ | |
683 | return wxGIF_TRUNCATED; | |
684 | } | |
685 | } | |
686 | ||
e4b8154a | 687 | return wxGIF_OK; |
464122b6 JS |
688 | } |
689 | ||
7be110e3 | 690 | #endif // wxUSE_STREAMS && wxUSE_GIF |