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