| 1 | ///////////////////////////////////////////////////////////////////////////// |
| 2 | // Name: gifdecod.cpp |
| 3 | // Purpose: wxGIFDecoder, GIF reader for wxImage and wxAnimation |
| 4 | // Author: Guillermo Rodriguez Garcia <guille@iies.es> |
| 5 | // Version: 3.04 |
| 6 | // RCS-ID: $Id$ |
| 7 | // Copyright: (c) Guillermo Rodriguez Garcia |
| 8 | // Licence: wxWindows licence |
| 9 | ///////////////////////////////////////////////////////////////////////////// |
| 10 | |
| 11 | // For compilers that support precompilation, includes "wx.h". |
| 12 | #include "wx/wxprec.h" |
| 13 | |
| 14 | #ifdef __BORLANDC__ |
| 15 | # pragma hdrstop |
| 16 | #endif |
| 17 | |
| 18 | #ifndef WX_PRECOMP |
| 19 | # include "wx/defs.h" |
| 20 | # include "wx/palette.h" |
| 21 | #endif |
| 22 | |
| 23 | #if wxUSE_STREAMS && wxUSE_GIF |
| 24 | |
| 25 | #include <stdlib.h> |
| 26 | #include <string.h> |
| 27 | #include "wx/gifdecod.h" |
| 28 | |
| 29 | |
| 30 | //--------------------------------------------------------------------------- |
| 31 | // GIFImage constructor |
| 32 | //--------------------------------------------------------------------------- |
| 33 | GIFImage::GIFImage() |
| 34 | { |
| 35 | w = 0; |
| 36 | h = 0; |
| 37 | left = 0; |
| 38 | top = 0; |
| 39 | transparent = 0; |
| 40 | disposal = 0; |
| 41 | delay = -1; |
| 42 | p = (unsigned char *) NULL; |
| 43 | pal = (unsigned char *) NULL; |
| 44 | next = (GIFImage *) NULL; |
| 45 | prev = (GIFImage *) NULL; |
| 46 | } |
| 47 | |
| 48 | //--------------------------------------------------------------------------- |
| 49 | // wxGIFDecoder constructor and destructor |
| 50 | //--------------------------------------------------------------------------- |
| 51 | |
| 52 | wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim) |
| 53 | { |
| 54 | m_f = s; |
| 55 | m_anim = anim; |
| 56 | |
| 57 | m_background = -1; |
| 58 | m_screenw = 0; |
| 59 | m_screenh = 0; |
| 60 | |
| 61 | m_pimage = NULL; |
| 62 | m_pfirst = NULL; |
| 63 | m_plast = NULL; |
| 64 | m_image = 0; |
| 65 | m_nimages = 0; |
| 66 | } |
| 67 | |
| 68 | wxGIFDecoder::~wxGIFDecoder() |
| 69 | { |
| 70 | Destroy(); |
| 71 | } |
| 72 | |
| 73 | void wxGIFDecoder::Destroy() |
| 74 | { |
| 75 | GIFImage *pimg, *paux; |
| 76 | |
| 77 | pimg = m_pfirst; |
| 78 | |
| 79 | while (pimg != NULL) |
| 80 | { |
| 81 | paux = pimg->next; |
| 82 | free(pimg->p); |
| 83 | free(pimg->pal); |
| 84 | delete pimg; |
| 85 | pimg = paux; |
| 86 | } |
| 87 | |
| 88 | m_pimage = NULL; |
| 89 | m_pfirst = NULL; |
| 90 | m_plast = NULL; |
| 91 | m_image = 0; |
| 92 | m_nimages = 0; |
| 93 | } |
| 94 | |
| 95 | |
| 96 | //--------------------------------------------------------------------------- |
| 97 | // Convert this image to a wxImage object |
| 98 | //--------------------------------------------------------------------------- |
| 99 | |
| 100 | // This function was designed by Vaclav Slavik |
| 101 | |
| 102 | bool wxGIFDecoder::ConvertToImage(wxImage *image) const |
| 103 | { |
| 104 | unsigned char *src, *dst, *pal; |
| 105 | unsigned long i; |
| 106 | int transparent; |
| 107 | |
| 108 | /* just in case... */ |
| 109 | image->Destroy(); |
| 110 | |
| 111 | /* create the image */ |
| 112 | image->Create(GetWidth(), GetHeight()); |
| 113 | |
| 114 | if (!image->Ok()) |
| 115 | return false; |
| 116 | |
| 117 | pal = GetPalette(); |
| 118 | src = GetData(); |
| 119 | dst = image->GetData(); |
| 120 | transparent = GetTransparentColour(); |
| 121 | |
| 122 | /* set transparent colour mask */ |
| 123 | if (transparent != -1) |
| 124 | { |
| 125 | for (i = 0; i < 256; i++) |
| 126 | { |
| 127 | if ((pal[3 * i + 0] == 255) && |
| 128 | (pal[3 * i + 1] == 0) && |
| 129 | (pal[3 * i + 2] == 255)) |
| 130 | { |
| 131 | pal[3 * i + 2] = 254; |
| 132 | } |
| 133 | } |
| 134 | |
| 135 | pal[3 * transparent + 0] = 255, |
| 136 | pal[3 * transparent + 1] = 0, |
| 137 | pal[3 * transparent + 2] = 255; |
| 138 | |
| 139 | image->SetMaskColour(255, 0, 255); |
| 140 | } |
| 141 | else |
| 142 | image->SetMask(false); |
| 143 | |
| 144 | #if wxUSE_PALETTE |
| 145 | unsigned char r[256]; |
| 146 | unsigned char g[256]; |
| 147 | unsigned char b[256]; |
| 148 | |
| 149 | for (i = 0; i < 256; i++) |
| 150 | { |
| 151 | r[i] = pal[3*i + 0]; |
| 152 | g[i] = pal[3*i + 1]; |
| 153 | b[i] = pal[3*i + 2]; |
| 154 | } |
| 155 | |
| 156 | image->SetPalette(wxPalette(256, r, g, b)); |
| 157 | #endif // wxUSE_PALETTE |
| 158 | |
| 159 | /* copy image data */ |
| 160 | for (i = 0; i < (GetWidth() * GetHeight()); i++, src++) |
| 161 | { |
| 162 | *(dst++) = pal[3 * (*src) + 0]; |
| 163 | *(dst++) = pal[3 * (*src) + 1]; |
| 164 | *(dst++) = pal[3 * (*src) + 2]; |
| 165 | } |
| 166 | |
| 167 | return true; |
| 168 | } |
| 169 | |
| 170 | |
| 171 | //--------------------------------------------------------------------------- |
| 172 | // Data accessors |
| 173 | //--------------------------------------------------------------------------- |
| 174 | |
| 175 | // Get data for current frame |
| 176 | |
| 177 | int wxGIFDecoder::GetFrameIndex() const { return m_image; } |
| 178 | unsigned char* wxGIFDecoder::GetData() const { return (m_pimage->p); } |
| 179 | unsigned char* wxGIFDecoder::GetPalette() const { return (m_pimage->pal); } |
| 180 | unsigned int wxGIFDecoder::GetWidth() const { return (m_pimage->w); } |
| 181 | unsigned int wxGIFDecoder::GetHeight() const { return (m_pimage->h); } |
| 182 | unsigned int wxGIFDecoder::GetTop() const { return (m_pimage->top); } |
| 183 | unsigned int wxGIFDecoder::GetLeft() const { return (m_pimage->left); } |
| 184 | int wxGIFDecoder::GetTransparentColour() const { return (m_pimage->transparent); } |
| 185 | int wxGIFDecoder::GetDisposalMethod() const { return (m_pimage->disposal); } |
| 186 | long wxGIFDecoder::GetDelay() const { return (m_pimage->delay); } |
| 187 | |
| 188 | // Get global data |
| 189 | |
| 190 | unsigned int wxGIFDecoder::GetLogicalScreenWidth() const { return m_screenw; } |
| 191 | unsigned int wxGIFDecoder::GetLogicalScreenHeight() const { return m_screenh; } |
| 192 | int wxGIFDecoder::GetBackgroundColour() const { return m_background; } |
| 193 | int wxGIFDecoder::GetNumberOfFrames() const { return m_nimages; } |
| 194 | bool wxGIFDecoder::IsAnimation() const { return (m_nimages > 1); } |
| 195 | |
| 196 | |
| 197 | //--------------------------------------------------------------------------- |
| 198 | // Functions to move through the animation |
| 199 | //--------------------------------------------------------------------------- |
| 200 | |
| 201 | bool wxGIFDecoder::GoFirstFrame() |
| 202 | { |
| 203 | if (!IsAnimation()) |
| 204 | return false; |
| 205 | |
| 206 | m_image = 1; |
| 207 | m_pimage = m_pfirst; |
| 208 | return true; |
| 209 | } |
| 210 | |
| 211 | bool wxGIFDecoder::GoLastFrame() |
| 212 | { |
| 213 | if (!IsAnimation()) |
| 214 | return false; |
| 215 | |
| 216 | m_image = m_nimages; |
| 217 | m_pimage = m_plast; |
| 218 | return true; |
| 219 | } |
| 220 | |
| 221 | bool wxGIFDecoder::GoNextFrame(bool cyclic) |
| 222 | { |
| 223 | if (!IsAnimation()) |
| 224 | return false; |
| 225 | |
| 226 | if ((m_image < m_nimages) || (cyclic)) |
| 227 | { |
| 228 | m_pimage = m_pimage->next; |
| 229 | m_image++; |
| 230 | |
| 231 | if (!m_pimage) |
| 232 | { |
| 233 | m_image = 1; |
| 234 | m_pimage = m_pfirst; |
| 235 | } |
| 236 | |
| 237 | return true; |
| 238 | } |
| 239 | else |
| 240 | return false; |
| 241 | } |
| 242 | |
| 243 | bool wxGIFDecoder::GoPrevFrame(bool cyclic) |
| 244 | { |
| 245 | if (!IsAnimation()) |
| 246 | return false; |
| 247 | |
| 248 | if ((m_image > 1) || (cyclic)) |
| 249 | { |
| 250 | m_pimage = m_pimage->prev; |
| 251 | m_image--; |
| 252 | |
| 253 | if (!m_pimage) |
| 254 | { |
| 255 | m_image = m_nimages; |
| 256 | m_pimage = m_plast; |
| 257 | } |
| 258 | |
| 259 | return true; |
| 260 | } |
| 261 | else |
| 262 | return false; |
| 263 | } |
| 264 | |
| 265 | bool wxGIFDecoder::GoFrame(int which) |
| 266 | { |
| 267 | if (!IsAnimation()) |
| 268 | return false; |
| 269 | |
| 270 | if ((which >= 1) && (which <= m_nimages)) |
| 271 | { |
| 272 | m_image = 1; |
| 273 | m_pimage = m_pfirst; |
| 274 | |
| 275 | while (m_image < which) |
| 276 | { |
| 277 | m_image++; |
| 278 | m_pimage = m_pimage->next; |
| 279 | } |
| 280 | |
| 281 | return true; |
| 282 | } |
| 283 | else |
| 284 | return false; |
| 285 | } |
| 286 | |
| 287 | |
| 288 | //--------------------------------------------------------------------------- |
| 289 | // GIF reading and decoding |
| 290 | //--------------------------------------------------------------------------- |
| 291 | |
| 292 | // getcode: |
| 293 | // Reads the next code from the file stream, with size 'bits' |
| 294 | // |
| 295 | int wxGIFDecoder::getcode(int bits, int ab_fin) |
| 296 | { |
| 297 | unsigned int mask; /* bit mask */ |
| 298 | unsigned int code; /* code (result) */ |
| 299 | |
| 300 | |
| 301 | /* get remaining bits from last byte read */ |
| 302 | mask = (1 << bits) - 1; |
| 303 | code = (m_lastbyte >> (8 - m_restbits)) & mask; |
| 304 | |
| 305 | /* keep reading new bytes while needed */ |
| 306 | while (bits > m_restbits) |
| 307 | { |
| 308 | /* if no bytes left in this block, read the next block */ |
| 309 | if (m_restbyte == 0) |
| 310 | { |
| 311 | m_restbyte = (unsigned char)m_f->GetC(); |
| 312 | |
| 313 | /* Some encoders are a bit broken: instead of issuing |
| 314 | * an end-of-image symbol (ab_fin) they come up with |
| 315 | * a zero-length subblock!! We catch this here so |
| 316 | * that the decoder sees an ab_fin code. |
| 317 | */ |
| 318 | if (m_restbyte == 0) |
| 319 | { |
| 320 | code = ab_fin; |
| 321 | break; |
| 322 | } |
| 323 | |
| 324 | /* prefetch data */ |
| 325 | m_f->Read((void *) m_buffer, m_restbyte); |
| 326 | if (m_f->LastRead() != m_restbyte) |
| 327 | { |
| 328 | code = ab_fin; |
| 329 | return code; |
| 330 | } |
| 331 | m_bufp = m_buffer; |
| 332 | } |
| 333 | |
| 334 | /* read next byte and isolate the bits we need */ |
| 335 | m_lastbyte = (unsigned char) (*m_bufp++); |
| 336 | mask = (1 << (bits - m_restbits)) - 1; |
| 337 | code = code + ((m_lastbyte & mask) << m_restbits); |
| 338 | m_restbyte--; |
| 339 | |
| 340 | /* adjust total number of bits extracted from the buffer */ |
| 341 | m_restbits = m_restbits + 8; |
| 342 | } |
| 343 | |
| 344 | /* find number of bits remaining for next code */ |
| 345 | m_restbits = (m_restbits - bits); |
| 346 | |
| 347 | return code; |
| 348 | } |
| 349 | |
| 350 | |
| 351 | // dgif: |
| 352 | // GIF decoding function. The initial code size (aka root size) |
| 353 | // is 'bits'. Supports interlaced images (interl == 1). |
| 354 | // Returns wxGIF_OK (== 0) on success, or an error code if something |
| 355 | // fails (see header file for details) |
| 356 | int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits) |
| 357 | { |
| 358 | static const int allocSize = 4096 + 1; |
| 359 | int *ab_prefix = new int[allocSize]; /* alphabet (prefixes) */ |
| 360 | if (ab_prefix == NULL) |
| 361 | { |
| 362 | return wxGIF_MEMERR; |
| 363 | } |
| 364 | |
| 365 | int *ab_tail = new int[allocSize]; /* alphabet (tails) */ |
| 366 | if (ab_tail == NULL) |
| 367 | { |
| 368 | delete[] ab_prefix; |
| 369 | return wxGIF_MEMERR; |
| 370 | } |
| 371 | |
| 372 | int *stack = new int[allocSize]; /* decompression stack */ |
| 373 | if (stack == NULL) |
| 374 | { |
| 375 | delete[] ab_prefix; |
| 376 | delete[] ab_tail; |
| 377 | return wxGIF_MEMERR; |
| 378 | } |
| 379 | |
| 380 | int ab_clr; /* clear code */ |
| 381 | int ab_fin; /* end of info code */ |
| 382 | int ab_bits; /* actual symbol width, in bits */ |
| 383 | int ab_free; /* first free position in alphabet */ |
| 384 | int ab_max; /* last possible character in alphabet */ |
| 385 | int pass; /* pass number in interlaced images */ |
| 386 | int pos; /* index into decompresion stack */ |
| 387 | unsigned int x, y; /* position in image buffer */ |
| 388 | |
| 389 | int code, readcode, lastcode, abcabca; |
| 390 | |
| 391 | /* these won't change */ |
| 392 | ab_clr = (1 << bits); |
| 393 | ab_fin = (1 << bits) + 1; |
| 394 | |
| 395 | /* these will change through the decompression proccess */ |
| 396 | ab_bits = bits + 1; |
| 397 | ab_free = (1 << bits) + 2; |
| 398 | ab_max = (1 << ab_bits) - 1; |
| 399 | lastcode = -1; |
| 400 | abcabca = -1; |
| 401 | pass = 1; |
| 402 | pos = x = y = 0; |
| 403 | |
| 404 | /* reset decoder vars */ |
| 405 | m_restbits = 0; |
| 406 | m_restbyte = 0; |
| 407 | m_lastbyte = 0; |
| 408 | |
| 409 | do |
| 410 | { |
| 411 | /* get next code */ |
| 412 | readcode = code = getcode(ab_bits, ab_fin); |
| 413 | |
| 414 | /* end of image? */ |
| 415 | if (code == ab_fin) break; |
| 416 | |
| 417 | /* reset alphabet? */ |
| 418 | if (code == ab_clr) |
| 419 | { |
| 420 | /* reset main variables */ |
| 421 | ab_bits = bits + 1; |
| 422 | ab_free = (1 << bits) + 2; |
| 423 | ab_max = (1 << ab_bits) - 1; |
| 424 | lastcode = -1; |
| 425 | abcabca = -1; |
| 426 | |
| 427 | /* skip to next code */ |
| 428 | continue; |
| 429 | } |
| 430 | |
| 431 | /* unknown code: special case (like in ABCABCA) */ |
| 432 | if (code >= ab_free) |
| 433 | { |
| 434 | code = lastcode; /* take last string */ |
| 435 | stack[pos++] = abcabca; /* add first character */ |
| 436 | } |
| 437 | |
| 438 | /* build the string for this code in the stack */ |
| 439 | while (code > ab_clr) |
| 440 | { |
| 441 | stack[pos++] = ab_tail[code]; |
| 442 | code = ab_prefix[code]; |
| 443 | |
| 444 | // Don't overflow. This shouldn't happen with normal |
| 445 | // GIF files, the allocSize of 4096+1 is enough. This |
| 446 | // will only happen with badly formed GIFs. |
| 447 | if (pos >= allocSize) |
| 448 | { |
| 449 | delete[] ab_prefix; |
| 450 | delete[] ab_tail; |
| 451 | delete[] stack; |
| 452 | return wxGIF_INVFORMAT; |
| 453 | } |
| 454 | } |
| 455 | |
| 456 | if (pos >= allocSize) |
| 457 | { |
| 458 | delete[] ab_prefix; |
| 459 | delete[] ab_tail; |
| 460 | delete[] stack; |
| 461 | return wxGIF_INVFORMAT; |
| 462 | } |
| 463 | |
| 464 | stack[pos] = code; /* push last code into the stack */ |
| 465 | abcabca = code; /* save for special case */ |
| 466 | |
| 467 | /* make new entry in alphabet (only if NOT just cleared) */ |
| 468 | if (lastcode != -1) |
| 469 | { |
| 470 | ab_prefix[ab_free] = lastcode; |
| 471 | ab_tail[ab_free] = code; |
| 472 | ab_free++; |
| 473 | |
| 474 | if ((ab_free > ab_max) && (ab_bits < 12)) |
| 475 | { |
| 476 | ab_bits++; |
| 477 | ab_max = (1 << ab_bits) - 1; |
| 478 | } |
| 479 | } |
| 480 | |
| 481 | /* dump stack data to the image buffer */ |
| 482 | while (pos >= 0) |
| 483 | { |
| 484 | (img->p)[x + (y * (img->w))] = (char) stack[pos]; |
| 485 | pos--; |
| 486 | |
| 487 | if (++x >= (img->w)) |
| 488 | { |
| 489 | x = 0; |
| 490 | |
| 491 | if (interl) |
| 492 | { |
| 493 | /* support for interlaced images */ |
| 494 | switch (pass) |
| 495 | { |
| 496 | case 1: y += 8; break; |
| 497 | case 2: y += 8; break; |
| 498 | case 3: y += 4; break; |
| 499 | case 4: y += 2; break; |
| 500 | } |
| 501 | |
| 502 | /* loop until a valid y coordinate has been |
| 503 | found, Or if the maximum number of passes has |
| 504 | been reached, exit the loop, and stop image |
| 505 | decoding (At this point the image is successfully |
| 506 | decoded). |
| 507 | If we don't loop, but merely set y to some other |
| 508 | value, that new value might still be invalid depending |
| 509 | on the height of the image. This would cause out of |
| 510 | bounds writing. |
| 511 | */ |
| 512 | while (y >= (img->h)) |
| 513 | { |
| 514 | switch (++pass) |
| 515 | { |
| 516 | case 2: y = 4; break; |
| 517 | case 3: y = 2; break; |
| 518 | case 4: y = 1; break; |
| 519 | |
| 520 | default: |
| 521 | /* |
| 522 | It's possible we arrive here. For example this |
| 523 | happens when the image is interlaced, and the |
| 524 | height is 1. Looking at the above cases, the |
| 525 | lowest possible y is 1. While the only valid |
| 526 | one would be 0 for an image of height 1. So |
| 527 | 'eventually' the loop will arrive here. |
| 528 | This case makes sure this while loop is |
| 529 | exited, as well as the 2 other ones. |
| 530 | */ |
| 531 | |
| 532 | // Set y to a valid coordinate so the local |
| 533 | // while loop will be exited. (y = 0 always |
| 534 | // is >= img->h since if img->h == 0 the |
| 535 | // image is never decoded) |
| 536 | y = 0; |
| 537 | |
| 538 | // This will exit the other outer while loop |
| 539 | pos = -1; |
| 540 | |
| 541 | // This will halt image decoding. |
| 542 | code = ab_fin; |
| 543 | |
| 544 | break; |
| 545 | } |
| 546 | } |
| 547 | } |
| 548 | else |
| 549 | { |
| 550 | /* non-interlaced */ |
| 551 | y++; |
| 552 | /* |
| 553 | Normally image decoding is finished when an End of Information code is |
| 554 | encountered (code == ab_fin) however some broken encoders write wrong |
| 555 | "block byte counts" (The first byte value after the "code size" byte), |
| 556 | being one value too high. It might very well be possible other variants |
| 557 | of this problem occur as well. The only sensible solution seems to |
| 558 | be to check for clipping. |
| 559 | Example of wrong encoding: |
| 560 | (1 * 1 B/W image, raster data stream follows in hex bytes) |
| 561 | |
| 562 | 02 << B/W images have a code size of 2 |
| 563 | 02 << Block byte count |
| 564 | 44 << LZW packed |
| 565 | 00 << Zero byte count (terminates data stream) |
| 566 | |
| 567 | Because the block byte count is 2, the zero byte count is used in the |
| 568 | decoding process, and decoding is continued after this byte. (While it |
| 569 | should signal an end of image) |
| 570 | |
| 571 | It should be: |
| 572 | 02 |
| 573 | 02 |
| 574 | 44 |
| 575 | 01 << When decoded this correctly includes the End of Information code |
| 576 | 00 |
| 577 | |
| 578 | Or (Worse solution): |
| 579 | 02 |
| 580 | 01 |
| 581 | 44 |
| 582 | 00 |
| 583 | (The 44 doesn't include an End of Information code, but at least the |
| 584 | decoder correctly skips to 00 now after decoding, and signals this |
| 585 | as an End of Information itself) |
| 586 | */ |
| 587 | if (y >= img->h) |
| 588 | { |
| 589 | code = ab_fin; |
| 590 | break; |
| 591 | } |
| 592 | } |
| 593 | } |
| 594 | } |
| 595 | |
| 596 | pos = 0; |
| 597 | lastcode = readcode; |
| 598 | } |
| 599 | while (code != ab_fin); |
| 600 | |
| 601 | delete [] ab_prefix ; |
| 602 | delete [] ab_tail ; |
| 603 | delete [] stack ; |
| 604 | |
| 605 | return wxGIF_OK; |
| 606 | } |
| 607 | |
| 608 | |
| 609 | // CanRead: |
| 610 | // Returns true if the file looks like a valid GIF, false otherwise. |
| 611 | // |
| 612 | bool wxGIFDecoder::CanRead() |
| 613 | { |
| 614 | unsigned char buf[3]; |
| 615 | |
| 616 | if ( !m_f->Read(buf, WXSIZEOF(buf)) ) |
| 617 | return false; |
| 618 | |
| 619 | m_f->SeekI(-(wxFileOffset)WXSIZEOF(buf), wxFromCurrent); |
| 620 | |
| 621 | return memcmp(buf, "GIF", WXSIZEOF(buf)) == 0; |
| 622 | } |
| 623 | |
| 624 | |
| 625 | // ReadGIF: |
| 626 | // Reads and decodes one or more GIF images, depending on whether |
| 627 | // animated GIF support is enabled. Can read GIFs with any bit |
| 628 | // size (color depth), but the output images are always expanded |
| 629 | // to 8 bits per pixel. Also, the image palettes always contain |
| 630 | // 256 colors, although some of them may be unused. Returns wxGIF_OK |
| 631 | // (== 0) on success, or an error code if something fails (see |
| 632 | // header file for details) |
| 633 | // |
| 634 | int wxGIFDecoder::ReadGIF() |
| 635 | { |
| 636 | unsigned int ncolors; |
| 637 | int bits, interl, transparent, disposal, i; |
| 638 | long size; |
| 639 | long delay; |
| 640 | unsigned char type = 0; |
| 641 | unsigned char pal[768]; |
| 642 | unsigned char buf[16]; |
| 643 | GIFImage **ppimg; |
| 644 | GIFImage *pimg, *pprev; |
| 645 | |
| 646 | /* check GIF signature */ |
| 647 | if (!CanRead()) |
| 648 | return wxGIF_INVFORMAT; |
| 649 | |
| 650 | /* check for animated GIF support (ver. >= 89a) */ |
| 651 | |
| 652 | static const size_t headerSize = (3 + 3); |
| 653 | m_f->Read(buf, headerSize); |
| 654 | if (m_f->LastRead() != headerSize) |
| 655 | { |
| 656 | return wxGIF_INVFORMAT; |
| 657 | } |
| 658 | |
| 659 | if (memcmp(buf + 3, "89a", 3) < 0) |
| 660 | { |
| 661 | m_anim = false; |
| 662 | } |
| 663 | |
| 664 | /* read logical screen descriptor block (LSDB) */ |
| 665 | static const size_t lsdbSize = (2 + 2 + 1 + 1 + 1); |
| 666 | m_f->Read(buf, lsdbSize); |
| 667 | if (m_f->LastRead() != lsdbSize) |
| 668 | { |
| 669 | return wxGIF_INVFORMAT; |
| 670 | } |
| 671 | |
| 672 | m_screenw = buf[0] + 256 * buf[1]; |
| 673 | m_screenh = buf[2] + 256 * buf[3]; |
| 674 | |
| 675 | if ((m_screenw == 0) || (m_screenh == 0)) |
| 676 | { |
| 677 | return wxGIF_INVFORMAT; |
| 678 | } |
| 679 | |
| 680 | /* load global color map if available */ |
| 681 | if ((buf[4] & 0x80) == 0x80) |
| 682 | { |
| 683 | m_background = buf[5]; |
| 684 | |
| 685 | ncolors = 2 << (buf[4] & 0x07); |
| 686 | size_t numBytes = 3 * ncolors; |
| 687 | m_f->Read(pal, numBytes); |
| 688 | if (m_f->LastRead() != numBytes) |
| 689 | { |
| 690 | return wxGIF_INVFORMAT; |
| 691 | } |
| 692 | } |
| 693 | |
| 694 | /* transparent colour, disposal method and delay default to unused */ |
| 695 | transparent = -1; |
| 696 | disposal = -1; |
| 697 | delay = -1; |
| 698 | |
| 699 | /* read images */ |
| 700 | ppimg = &m_pfirst; |
| 701 | pprev = NULL; |
| 702 | pimg = NULL; |
| 703 | |
| 704 | bool done = false; |
| 705 | |
| 706 | while (!done) |
| 707 | { |
| 708 | type = (unsigned char)m_f->GetC(); |
| 709 | |
| 710 | /* |
| 711 | If the end of file has been reached (or an error) and a ";" |
| 712 | (0x3B) hasn't been encountered yet, exit the loop. (Without this |
| 713 | check the while loop would loop endlessly.) Later on, in the next while |
| 714 | loop, the file will be treated as being truncated (But still |
| 715 | be decoded as far as possible). returning wxGIF_TRUNCATED is not |
| 716 | possible here since some init code is done after this loop. |
| 717 | */ |
| 718 | if (m_f->Eof())// || !m_f->IsOk()) |
| 719 | { |
| 720 | /* |
| 721 | type is set to some bogus value, so there's no |
| 722 | need to continue evaluating it. |
| 723 | */ |
| 724 | break; // Alternative : "return wxGIF_INVFORMAT;" |
| 725 | } |
| 726 | |
| 727 | /* end of data? */ |
| 728 | if (type == 0x3B) |
| 729 | { |
| 730 | done = true; |
| 731 | } |
| 732 | else |
| 733 | /* extension block? */ |
| 734 | if (type == 0x21) |
| 735 | { |
| 736 | if (((unsigned char)m_f->GetC()) == 0xF9) |
| 737 | /* graphics control extension, parse it */ |
| 738 | { |
| 739 | static const size_t gceSize = 6; |
| 740 | m_f->Read(buf, gceSize); |
| 741 | if (m_f->LastRead() != gceSize) |
| 742 | { |
| 743 | Destroy(); |
| 744 | return wxGIF_INVFORMAT; |
| 745 | } |
| 746 | |
| 747 | /* read delay and convert from 1/100 of a second to ms */ |
| 748 | delay = 10 * (buf[2] + 256 * buf[3]); |
| 749 | |
| 750 | /* read transparent colour index, if used */ |
| 751 | if (buf[1] & 0x01) |
| 752 | transparent = buf[4]; |
| 753 | |
| 754 | /* read disposal method */ |
| 755 | disposal = ((buf[1] & 0x1C) >> 2) - 1; |
| 756 | } |
| 757 | else |
| 758 | /* other extension, skip */ |
| 759 | { |
| 760 | while ((i = (unsigned char)m_f->GetC()) != 0) |
| 761 | { |
| 762 | m_f->SeekI(i, wxFromCurrent); |
| 763 | if (m_f->Eof()) |
| 764 | { |
| 765 | done = true; |
| 766 | break; |
| 767 | } |
| 768 | } |
| 769 | } |
| 770 | } |
| 771 | else |
| 772 | /* image descriptor block? */ |
| 773 | if (type == 0x2C) |
| 774 | { |
| 775 | /* allocate memory for IMAGEN struct */ |
| 776 | pimg = (*ppimg) = new GIFImage(); |
| 777 | |
| 778 | if (pimg == NULL) |
| 779 | { |
| 780 | Destroy(); |
| 781 | return wxGIF_MEMERR; |
| 782 | } |
| 783 | |
| 784 | /* fill in the data */ |
| 785 | static const size_t idbSize = (2 + 2 + 2 + 2 + 1); |
| 786 | m_f->Read(buf, idbSize); |
| 787 | if (m_f->LastRead() != idbSize) |
| 788 | { |
| 789 | Destroy(); |
| 790 | return wxGIF_INVFORMAT; |
| 791 | } |
| 792 | |
| 793 | pimg->left = buf[0] + 256 * buf[1]; |
| 794 | pimg->top = buf[2] + 256 * buf[3]; |
| 795 | /* |
| 796 | pimg->left = buf[4] + 256 * buf[5]; |
| 797 | pimg->top = buf[4] + 256 * buf[5]; |
| 798 | */ |
| 799 | pimg->w = buf[4] + 256 * buf[5]; |
| 800 | pimg->h = buf[6] + 256 * buf[7]; |
| 801 | |
| 802 | if ((pimg->w == 0) || (pimg->w > m_screenw) || (pimg->h == 0) || (pimg->h > m_screenh)) |
| 803 | { |
| 804 | Destroy(); |
| 805 | return wxGIF_INVFORMAT; |
| 806 | } |
| 807 | |
| 808 | interl = ((buf[8] & 0x40)? 1 : 0); |
| 809 | size = pimg->w * pimg->h; |
| 810 | |
| 811 | pimg->transparent = transparent; |
| 812 | pimg->disposal = disposal; |
| 813 | pimg->delay = delay; |
| 814 | pimg->next = NULL; |
| 815 | pimg->prev = pprev; |
| 816 | pprev = pimg; |
| 817 | ppimg = &pimg->next; |
| 818 | |
| 819 | /* allocate memory for image and palette */ |
| 820 | pimg->p = (unsigned char *) malloc((size_t)size); |
| 821 | pimg->pal = (unsigned char *) malloc(768); |
| 822 | |
| 823 | if ((!pimg->p) || (!pimg->pal)) |
| 824 | { |
| 825 | Destroy(); |
| 826 | return wxGIF_MEMERR; |
| 827 | } |
| 828 | |
| 829 | /* load local color map if available, else use global map */ |
| 830 | if ((buf[8] & 0x80) == 0x80) |
| 831 | { |
| 832 | ncolors = 2 << (buf[8] & 0x07); |
| 833 | size_t numBytes = 3 * ncolors; |
| 834 | m_f->Read(pimg->pal, numBytes); |
| 835 | if (m_f->LastRead() != numBytes) |
| 836 | { |
| 837 | Destroy(); |
| 838 | return wxGIF_INVFORMAT; |
| 839 | } |
| 840 | } |
| 841 | else |
| 842 | { |
| 843 | memcpy(pimg->pal, pal, 768); |
| 844 | } |
| 845 | |
| 846 | /* get initial code size from first byte in raster data */ |
| 847 | bits = (unsigned char)m_f->GetC(); |
| 848 | if (bits == 0) |
| 849 | { |
| 850 | Destroy(); |
| 851 | return wxGIF_INVFORMAT; |
| 852 | } |
| 853 | |
| 854 | /* decode image */ |
| 855 | int result = dgif(pimg, interl, bits); |
| 856 | if (result != wxGIF_OK) |
| 857 | { |
| 858 | Destroy(); |
| 859 | return result; |
| 860 | } |
| 861 | m_nimages++; |
| 862 | |
| 863 | /* if this is not an animated GIF, exit after first image */ |
| 864 | if (!m_anim) |
| 865 | done = true; |
| 866 | } |
| 867 | } |
| 868 | |
| 869 | if (m_nimages <= 0) |
| 870 | { |
| 871 | Destroy(); |
| 872 | return wxGIF_INVFORMAT; |
| 873 | } |
| 874 | |
| 875 | /* setup image pointers */ |
| 876 | m_image = 1; |
| 877 | m_plast = pimg; |
| 878 | m_pimage = m_pfirst; |
| 879 | |
| 880 | /* try to read to the end of the stream */ |
| 881 | while (type != 0x3B) |
| 882 | { |
| 883 | if (!m_f->IsOk()) |
| 884 | return wxGIF_TRUNCATED; |
| 885 | |
| 886 | type = (unsigned char)m_f->GetC(); |
| 887 | |
| 888 | if (type == 0x21) |
| 889 | { |
| 890 | /* extension type */ |
| 891 | (void) m_f->GetC(); |
| 892 | |
| 893 | /* skip all data */ |
| 894 | while ((i = (unsigned char)m_f->GetC()) != 0) |
| 895 | { |
| 896 | m_f->SeekI(i, wxFromCurrent); |
| 897 | } |
| 898 | } |
| 899 | else if (type == 0x2C) |
| 900 | { |
| 901 | /* image descriptor block */ |
| 902 | static const size_t idbSize = (2 + 2 + 2 + 2 + 1); |
| 903 | m_f->Read(buf, idbSize); |
| 904 | if (m_f->LastRead() != idbSize) |
| 905 | { |
| 906 | Destroy(); |
| 907 | return wxGIF_INVFORMAT; |
| 908 | } |
| 909 | |
| 910 | /* local color map */ |
| 911 | if ((buf[8] & 0x80) == 0x80) |
| 912 | { |
| 913 | ncolors = 2 << (buf[8] & 0x07); |
| 914 | wxFileOffset pos = m_f->TellI(); |
| 915 | wxFileOffset numBytes = 3 * ncolors; |
| 916 | m_f->SeekI(numBytes, wxFromCurrent); |
| 917 | if (m_f->TellI() != (pos + numBytes)) |
| 918 | { |
| 919 | Destroy(); |
| 920 | return wxGIF_INVFORMAT; |
| 921 | } |
| 922 | } |
| 923 | |
| 924 | /* initial code size */ |
| 925 | (void) m_f->GetC(); |
| 926 | |
| 927 | /* skip all data */ |
| 928 | while ((i = (unsigned char)m_f->GetC()) != 0) |
| 929 | { |
| 930 | m_f->SeekI(i, wxFromCurrent); |
| 931 | } |
| 932 | } |
| 933 | else if ((type != 0x3B) && (type != 00)) /* testing */ |
| 934 | { |
| 935 | /* images are OK, but couldn't read to the end of the stream */ |
| 936 | return wxGIF_TRUNCATED; |
| 937 | } |
| 938 | } |
| 939 | |
| 940 | return wxGIF_OK; |
| 941 | } |
| 942 | |
| 943 | #endif // wxUSE_STREAMS && wxUSE_GIF |