src/common/gifdecod.cpp

   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 #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
  23 #  include "wx/defs.h"
  24 #endif
  25
  26 #if wxUSE_STREAMS && wxUSE_GIF
  27
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include "wx/gifdecod.h"
  31
  32
  33 //---------------------------------------------------------------------------
  34 // wxGIFDecoder constructor and destructor
  35 //---------------------------------------------------------------------------
  36
  37 wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim)
  38 {
  39     m_f    = s;
  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 {
  60     GIFImage *pimg, *paux;
  61
  62     pimg = m_pfirst;
  63
  64     while (pimg != NULL)
  65     {
  66         paux = pimg->next;
  67         free(pimg->p);
  68         free(pimg->pal);
  69         delete pimg;
  70         pimg = paux;
  71     }
  72
  73     m_pimage  = NULL;
  74     m_pfirst  = NULL;
  75     m_plast   = NULL;
  76     m_image   = 0;
  77     m_nimages = 0;
  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
  93     /* just in case... */
  94     image->Destroy();
  95
  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
 129 #if wxUSE_PALETTE
 130     if (pal)
 131     {
 132         unsigned char r[256];
 133         unsigned char g[256];
 134         unsigned char b[256];
 135
 136         for (i = 0; i < 256; i++)
 137         {
 138             r[i] = pal[3*i + 0];
 139             g[i] = pal[3*i + 1];
 140             b[i] = pal[3*i + 2];
 141         }
 142
 143         image->SetPalette(wxPalette(256, r, g, b));
 144     }
 145 #endif // wxUSE_PALETTE
 146
 147     /* copy image data */
 148     for (i = 0; i < (GetWidth() * GetHeight()); i++, src++)
 149     {
 150         *(dst++) = pal[3 * (*src) + 0];
 151         *(dst++) = pal[3 * (*src) + 1];
 152         *(dst++) = pal[3 * (*src) + 2];
 153     }
 154
 155     return TRUE;
 156 }
 157
 158
 159 //---------------------------------------------------------------------------
 160 // Data accessors
 161 //---------------------------------------------------------------------------
 162
 163 // Get data for current frame
 164
 165 int wxGIFDecoder::GetFrameIndex() const         { return m_image; }
 166 unsigned char* wxGIFDecoder::GetData() const    { return (m_pimage->p); }
 167 unsigned char* wxGIFDecoder::GetPalette() const { return (m_pimage->pal); }
 168 unsigned int wxGIFDecoder::GetWidth() const     { return (m_pimage->w); }
 169 unsigned int wxGIFDecoder::GetHeight() const    { return (m_pimage->h); }
 170 unsigned int wxGIFDecoder::GetTop() const       { return (m_pimage->top); }
 171 unsigned int wxGIFDecoder::GetLeft() const      { return (m_pimage->left); }
 172 int wxGIFDecoder::GetTransparentColour() const  { return (m_pimage->transparent); }
 173 int wxGIFDecoder::GetDisposalMethod() const     { return (m_pimage->disposal); }
 174 long wxGIFDecoder::GetDelay() const             { return (m_pimage->delay); }
 175
 176 // Get global data
 177
 178 unsigned int wxGIFDecoder::GetLogicalScreenWidth() const    { return m_screenw; }
 179 unsigned int wxGIFDecoder::GetLogicalScreenHeight() const   { return m_screenh; }
 180 int wxGIFDecoder::GetBackgroundColour() const   { return m_background; }
 181 int wxGIFDecoder::GetNumberOfFrames() const     { return m_nimages; }
 182 bool wxGIFDecoder::IsAnimation() const          { return (m_nimages > 1); }
 183
 184
 185 //---------------------------------------------------------------------------
 186 // Functions to move through the animation
 187 //---------------------------------------------------------------------------
 188
 189 bool wxGIFDecoder::GoFirstFrame()
 190 {
 191     if (!IsAnimation())
 192         return FALSE;
 193
 194     m_image = 1;
 195     m_pimage = m_pfirst;
 196     return TRUE;
 197 }
 198
 199 bool wxGIFDecoder::GoLastFrame()
 200 {
 201     if (!IsAnimation())
 202         return FALSE;
 203
 204     m_image = m_nimages;
 205     m_pimage = m_plast;
 206     return TRUE;
 207 }
 208
 209 bool wxGIFDecoder::GoNextFrame(bool cyclic)
 210 {
 211     if (!IsAnimation())
 212         return FALSE;
 213
 214     if ((m_image < m_nimages) || (cyclic))
 215     {
 216         m_pimage = m_pimage->next;
 217         m_image++;
 218
 219         if (!m_pimage)
 220         {
 221             m_image = 1;
 222             m_pimage = m_pfirst;
 223         }
 224
 225         return TRUE;
 226     }
 227     else
 228         return FALSE;
 229 }
 230
 231 bool wxGIFDecoder::GoPrevFrame(bool cyclic)
 232 {
 233     if (!IsAnimation())
 234         return FALSE;
 235
 236     if ((m_image > 1) || (cyclic))
 237     {
 238         m_pimage = m_pimage->prev;
 239         m_image--;
 240
 241         if (!m_pimage)
 242         {
 243             m_image = m_nimages;
 244             m_pimage = m_plast;
 245         }
 246
 247         return TRUE;
 248     }
 249     else
 250         return FALSE;
 251 }
 252
 253 bool wxGIFDecoder::GoFrame(int which)
 254 {
 255     int i;
 256
 257     if (!IsAnimation())
 258         return FALSE;
 259
 260     if ((which >= 1) && (which <= m_nimages))
 261     {
 262         m_pimage = m_pfirst;
 263
 264         for (i = 1; i < which; i++)
 265             m_pimage = m_pimage->next;
 266
 267         return TRUE;
 268     }
 269     else
 270         return FALSE;
 271 }
 272
 273
 274 //---------------------------------------------------------------------------
 275 // GIF reading and decoding
 276 //---------------------------------------------------------------------------
 277
 278 // getcode:
 279 //  Reads the next code from the file stream, with size 'bits'
 280 //
 281 int wxGIFDecoder::getcode(int bits, int ab_fin)
 282 {
 283     unsigned int mask;          /* bit mask */
 284     unsigned int code;          /* code (result) */
 285
 286
 287     /* get remaining bits from last byte read */
 288     mask = (1 << bits) - 1;
 289     code = (m_lastbyte >> (8 - m_restbits)) & mask;
 290
 291     /* keep reading new bytes while needed */
 292     while (bits > m_restbits)
 293     {
 294         /* if no bytes left in this block, read the next block */
 295         if (m_restbyte == 0)
 296         {
 297             m_restbyte = (unsigned char)m_f->GetC();
 298
 299             /* Some encoders are a bit broken: instead of issuing
 300              * an end-of-image symbol (ab_fin) they come up with
 301              * a zero-length subblock!! We catch this here so
 302              * that the decoder sees an ab_fin code.
 303              */
 304             if (m_restbyte == 0)
 305             {
 306                 code = ab_fin;
 307                 break;
 308             }
 309
 310             /* prefetch data */
 311             m_f->Read((void *) m_buffer, m_restbyte);
 312             m_bufp = m_buffer;
 313         }
 314
 315         /* read next byte and isolate the bits we need */
 316         m_lastbyte = (unsigned char) (*m_bufp++);
 317         mask       = (1 << (bits - m_restbits)) - 1;
 318         code       = code + ((m_lastbyte & mask) << m_restbits);
 319         m_restbyte--;
 320
 321         /* adjust total number of bits extracted from the buffer */
 322         m_restbits = m_restbits + 8;
 323     }
 324
 325     /* find number of bits remaining for next code */
 326     m_restbits = (m_restbits - bits);
 327
 328     return code;
 329 }
 330
 331
 332 // dgif:
 333 //  GIF decoding function. The initial code size (aka root size)
 334 //  is 'bits'. Supports interlaced images (interl == 1).
 335 //
 336 int wxGIFDecoder::dgif(GIFImage *img, int interl, int bits)
 337 {
 338     int *ab_prefix = new int[4096]; /* alphabet (prefixes) */
 339     int *ab_tail = new int[4096];   /* alphabet (tails) */
 340     int *stack = new int[4096];     /* decompression stack */
 341     int ab_clr;                     /* clear code */
 342     int ab_fin;                     /* end of info code */
 343     int ab_bits;                    /* actual symbol width, in bits */
 344     int ab_free;                    /* first free position in alphabet */
 345     int ab_max;                     /* last possible character in alphabet */
 346     int pass;                       /* pass number in interlaced images */
 347     int pos;                        /* index into decompresion stack */
 348     unsigned int x, y;              /* position in image buffer */
 349
 350     int code, readcode, lastcode, abcabca;
 351
 352     /* these won't change */
 353     ab_clr = (1 << bits);
 354     ab_fin = (1 << bits) + 1;
 355
 356     /* these will change through the decompression proccess */
 357     ab_bits  = bits + 1;
 358     ab_free  = (1 << bits) + 2;
 359     ab_max   = (1 << ab_bits) - 1;
 360     lastcode = -1;
 361     abcabca  = -1;
 362     pass     = 1;
 363     pos = x = y = 0;
 364
 365     /* reset decoder vars */
 366     m_restbits = 0;
 367     m_restbyte = 0;
 368     m_lastbyte = 0;
 369
 370     do
 371     {
 372         /* get next code */
 373         readcode = code = getcode(ab_bits, ab_fin);
 374
 375         /* end of image? */
 376         if (code == ab_fin) break;
 377
 378         /* reset alphabet? */
 379         if (code == ab_clr)
 380         {
 381             /* reset main variables */
 382             ab_bits  = bits + 1;
 383             ab_free  = (1 << bits) + 2;
 384             ab_max   = (1 << ab_bits) - 1;
 385             lastcode = -1;
 386             abcabca  = -1;
 387
 388             /* skip to next code */
 389             continue;
 390         }
 391
 392         /* unknown code: special case (like in ABCABCA) */
 393         if (code >= ab_free)
 394         {
 395             code = lastcode;            /* take last string */
 396             stack[pos++] = abcabca;     /* add first character */
 397         }
 398
 399         /* build the string for this code in the stack */
 400         while (code > ab_clr)
 401         {
 402             stack[pos++] = ab_tail[code];
 403             code         = ab_prefix[code];
 404         }
 405         stack[pos] = code;              /* push last code into the stack */
 406         abcabca    = code;              /* save for special case */
 407
 408         /* make new entry in alphabet (only if NOT just cleared) */
 409         if (lastcode != -1)
 410         {
 411             ab_prefix[ab_free] = lastcode;
 412             ab_tail[ab_free]   = code;
 413             ab_free++;
 414
 415             if ((ab_free > ab_max) && (ab_bits < 12))
 416             {
 417                 ab_bits++;
 418                 ab_max = (1 << ab_bits) - 1;
 419             }
 420         }
 421
 422         /* dump stack data to the buffer */
 423         while (pos >= 0)
 424         {
 425             (img->p)[x + (y * (img->w))] = (char)stack[pos--];
 426
 427             if (++x >= (img->w))
 428             {
 429                 x = 0;
 430
 431                 if (interl)
 432                 {
 433                     /* support for interlaced images */
 434                     switch (pass)
 435                     {
 436                         case 1: y += 8; break;
 437                         case 2: y += 8; break;
 438                         case 3: y += 4; break;
 439                         case 4: y += 2; break;
 440                     }
 441                     if (y >= (img->h))
 442                     {
 443                         switch (++pass)
 444                         {
 445                             case 2: y = 4; break;
 446                             case 3: y = 2; break;
 447                             case 4: y = 1; break;
 448                         }
 449                     }
 450                 }
 451                 else
 452                 {
 453                     /* non-interlaced */
 454                     y++;
 455                 }
 456             }
 457         }
 458
 459         pos = 0;
 460         lastcode = readcode;
 461     }
 462     while (code != ab_fin);
 463
 464     delete [] ab_prefix ;
 465     delete [] ab_tail ;
 466     delete [] stack ;
 467
 468     return 0;
 469 }
 470
 471
 472 // CanRead:
 473 //  Returns TRUE if the file looks like a valid GIF, FALSE otherwise.
 474 //
 475 bool wxGIFDecoder::CanRead()
 476 {
 477     unsigned char buf[3];
 478
 479     m_f->Read(buf, 3);
 480     m_f->SeekI(-3, wxFromCurrent);
 481
 482     return (memcmp(buf, "GIF", 3) == 0);
 483 }
 484
 485
 486 // ReadGIF:
 487 //  Reads and decodes one or more GIF images, depending on whether
 488 //  animated GIF support is enabled. Can read GIFs with any bit
 489 //  size (color depth), but the output images are always expanded
 490 //  to 8 bits per pixel. Also, the image palettes always contain
 491 //  256 colors, although some of them may be unused. Returns wxGIF_OK
 492 //  (== 0) on success, or an error code if something fails (see
 493 //  header file for details)
 494 //
 495 int wxGIFDecoder::ReadGIF()
 496 {
 497     int           ncolors, bits, interl, transparent, disposal, i;
 498     long          size;
 499     long          delay;
 500     unsigned char type = 0;
 501     unsigned char pal[768];
 502     unsigned char buf[16];
 503     GIFImage      **ppimg;
 504         GIFImage      *pimg, *pprev;
 505
 506     /* check GIF signature */
 507     if (!CanRead())
 508         return wxGIF_INVFORMAT;
 509
 510     /* check for animated GIF support (ver. >= 89a) */
 511     m_f->Read(buf, 6);
 512
 513     if (memcmp(buf + 3, "89a", 3) < 0)
 514         m_anim = FALSE;
 515
 516     /* read logical screen descriptor block (LSDB) */
 517     m_f->Read(buf, 7);
 518     m_screenw = buf[0] + 256 * buf[1];
 519     m_screenh = buf[2] + 256 * buf[3];
 520
 521     /* load global color map if available */
 522     if ((buf[4] & 0x80) == 0x80)
 523     {
 524         m_background = buf[5];
 525
 526         ncolors = 2 << (buf[4] & 0x07);
 527         m_f->Read(pal, 3 * ncolors);
 528     }
 529
 530     /* transparent colour, disposal method and delay default to unused */
 531     transparent = -1;
 532     disposal = -1;
 533     delay = -1;
 534
 535     /* read images */
 536     ppimg = &m_pfirst;
 537     pprev = NULL;
 538     pimg  = NULL;
 539
 540     bool done = FALSE;
 541
 542     while(!done)
 543     {
 544         type = (unsigned char)m_f->GetC();
 545
 546         /* end of data? */
 547         if (type == 0x3B)
 548         {
 549             done = TRUE;
 550         }
 551         else
 552         /* extension block? */
 553         if (type == 0x21)
 554         {
 555             if (((unsigned char)m_f->GetC()) == 0xF9)
 556             /* graphics control extension, parse it */
 557             {
 558                 m_f->Read(buf, 6);
 559
 560                 /* read delay and convert from 1/100 of a second to ms */
 561                 delay = 10 * (buf[2] + 256 * buf[3]);
 562
 563                 /* read transparent colour index, if used */
 564                 if (buf[1] & 0x01)
 565                     transparent = buf[4];
 566
 567                 /* read disposal method */
 568                 disposal = (buf[1] & 0x1C) - 1;
 569             }
 570             else
 571             /* other extension, skip */
 572             {
 573                 while ((i = (unsigned char)m_f->GetC()) != 0)
 574                 {
 575                     m_f->SeekI(i, wxFromCurrent);
 576                 }
 577             }
 578         }
 579         else
 580         /* image descriptor block? */
 581         if (type == 0x2C)
 582         {
 583             /* allocate memory for IMAGEN struct */
 584             pimg = (*ppimg) = new GIFImage();
 585
 586             if (pimg == NULL)
 587             {
 588                 Destroy();
 589                 return wxGIF_MEMERR;
 590             }
 591
 592             /* fill in the data */
 593             m_f->Read(buf, 9);
 594             pimg->left = buf[0] + 256 * buf[1];
 595             pimg->top = buf[2] + 256 * buf[3];
 596 /*
 597             pimg->left = buf[4] + 256 * buf[5];
 598             pimg->top = buf[4] + 256 * buf[5];
 599 */
 600             pimg->w = buf[4] + 256 * buf[5];
 601             pimg->h = buf[6] + 256 * buf[7];
 602             interl = ((buf[8] & 0x40)? 1 : 0);
 603             size = pimg->w * pimg->h;
 604
 605             pimg->transparent = transparent;
 606             pimg->disposal = disposal;
 607             pimg->delay = delay;
 608             pimg->next = NULL;
 609             pimg->prev = pprev;
 610             pprev = pimg;
 611             ppimg = &pimg->next;
 612
 613             /* allocate memory for image and palette */
 614             pimg->p   = (unsigned char *) malloc((size_t)size);
 615             pimg->pal = (unsigned char *) malloc(768);
 616
 617             if ((!pimg->p) || (!pimg->pal))
 618             {
 619                 Destroy();
 620                 return wxGIF_MEMERR;
 621             }
 622
 623             /* load local color map if available, else use global map */
 624             if ((buf[8] & 0x80) == 0x80)
 625             {
 626                 ncolors = 2 << (buf[8] & 0x07);
 627                 m_f->Read(pimg->pal, 3 * ncolors);
 628             }
 629             else
 630                 memcpy(pimg->pal, pal, 768);
 631
 632             /* get initial code size from first byte in raster data */
 633             bits = (unsigned char)m_f->GetC();
 634
 635             /* decode image */
 636             dgif(pimg, interl, bits);
 637             m_nimages++;
 638
 639             /* if this is not an animated GIF, exit after first image */
 640             if (!m_anim)
 641                 done = TRUE;
 642         }
 643     }
 644
 645     /* setup image pointers */
 646     if (m_nimages != 0)
 647     {
 648         m_image = 1;
 649         m_plast = pimg;
 650         m_pimage = m_pfirst;
 651     }
 652
 653     /* try to read to the end of the stream */
 654     while (type != 0x3B)
 655     {
 656         if (!m_f->IsOk())
 657             return wxGIF_TRUNCATED;
 658
 659         type = (unsigned char)m_f->GetC();
 660
 661         if (type == 0x21)
 662         {
 663             /* extension type */
 664             (void) m_f->GetC();
 665
 666             /* skip all data */
 667             while ((i = (unsigned char)m_f->GetC()) != 0)
 668             {
 669                 m_f->SeekI(i, wxFromCurrent);
 670             }
 671         }
 672         else if (type == 0x2C)
 673         {
 674             /* image descriptor block */
 675             m_f->Read(buf, 9);
 676
 677             /* local color map */
 678             if ((buf[8] & 0x80) == 0x80)
 679             {
 680                 ncolors = 2 << (buf[8] & 0x07);
 681                 m_f->SeekI(3 * ncolors, wxFromCurrent);
 682             }
 683
 684             /* initial code size */
 685             (void) m_f->GetC();
 686
 687             /* skip all data */
 688             while ((i = (unsigned char)m_f->GetC()) != 0)
 689             {
 690                 m_f->SeekI(i, wxFromCurrent);
 691             }
 692         }
 693         else if ((type != 0x3B) && (type != 00)) /* testing */
 694         {
 695             /* images are OK, but couldn't read to the end of the stream */
 696             return wxGIF_TRUNCATED;
 697         }
 698     }
 699
 700     return wxGIF_OK;
 701 }
 702
 703 #endif // wxUSE_STREAMS && wxUSE_GIF