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