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:     3.03
   6 // RCS-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     IMAGEN *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         free(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
 287         /* read next byte and isolate the bits we need */
 288         m_lastbyte = (unsigned char)m_f->GetC();
 289         mask       = (1 << (bits - m_restbits)) - 1;
 290         code       = code + ((m_lastbyte & mask) << m_restbits);
 291         m_restbyte--;
 292
 293         /* adjust total number of bits extracted from the buffer */
 294         m_restbits = m_restbits + 8;
 295     }
 296
 297     /* find number of bits remaining for next code */
 298     m_restbits = (m_restbits - bits);
 299
 300     return code;
 301 }
 302
 303
 304 // dgif:
 305 //  GIF decoding function. The initial code size (aka root size)
 306 //  is 'bits'. Supports interlaced images (interl == 1).
 307 //
 308 int wxGIFDecoder::dgif(IMAGEN *img, int interl, int bits)
 309 {
 310     int ab_prefix[4096];        /* alphabet (prefixes) */
 311     int ab_tail[4096];          /* alphabet (tails) */
 312     int stack[4096];            /* decompression stack */
 313
 314     int ab_clr;                 /* clear code */
 315     int ab_fin;                 /* end of info code */
 316     int ab_bits;                /* actual symbol width, in bits */
 317     int ab_free;                /* first free position in alphabet */
 318     int ab_max;                 /* last possible character in alphabet */
 319     int pass;                   /* pass number in interlaced images */
 320     int pos;                    /* index into decompresion stack */
 321     unsigned int x, y;          /* position in image buffer */
 322
 323     int code, readcode, lastcode, abcabca;
 324
 325     /* these won't change */
 326     ab_clr = (1 << bits);
 327     ab_fin = (1 << bits) + 1;
 328
 329     /* these will change through the decompression proccess */
 330     ab_bits  = bits + 1;
 331     ab_free  = (1 << bits) + 2;
 332     ab_max   = (1 << ab_bits) - 1;
 333     lastcode = -1;
 334     abcabca  = -1;
 335     pass     = 1;
 336     pos = x = y = 0;
 337
 338     /* reset static globals */
 339     m_restbits = 0;
 340     m_restbyte = 0;
 341     m_lastbyte = 0;
 342
 343     do
 344     {
 345         /* get next code */
 346         readcode = code = getcode(ab_bits, ab_fin);
 347
 348         /* end of image? */
 349         if (code == ab_fin) break;
 350
 351         /* reset alphabet? */
 352         if (code == ab_clr)
 353         {
 354             /* reset main variables */
 355             ab_bits  = bits + 1;
 356             ab_free  = (1 << bits) + 2;
 357             ab_max   = (1 << ab_bits) - 1;
 358             lastcode = -1;
 359             abcabca  = -1;
 360
 361             /* skip to next code */
 362             continue;
 363         }
 364
 365         /* unknown code: special case (like in ABCABCA) */
 366         if (code >= ab_free)
 367         {
 368             code = lastcode;            /* take last string */
 369             stack[pos++] = abcabca;     /* add first character */
 370         }
 371
 372         /* build the string for this code in the stack */
 373         while (code > ab_clr)
 374         {
 375             stack[pos++] = ab_tail[code];
 376             code         = ab_prefix[code];
 377         }
 378         stack[pos] = code;              /* push last code into the stack */
 379         abcabca    = code;              /* save for special case */
 380
 381         /* make new entry in alphabet (only if NOT just cleared) */
 382         if (lastcode != -1)
 383         {
 384             ab_prefix[ab_free] = lastcode;
 385             ab_tail[ab_free]   = code;
 386             ab_free++;
 387
 388             if ((ab_free > ab_max) && (ab_bits < 12))
 389             {
 390                 ab_bits++;
 391                 ab_max = (1 << ab_bits) - 1;
 392             }
 393         }
 394
 395         /* dump stack data to the buffer */
 396         while (pos >= 0)
 397         {
 398             (img->p)[x + (y * (img->w))] = (char)stack[pos--];
 399
 400             if (++x >= (img->w))
 401             {
 402                 x = 0;
 403
 404                 if (interl)
 405                 {
 406                     /* support for interlaced images */
 407                     switch (pass)
 408                     {
 409                         case 1: y += 8; break;
 410                         case 2: y += 8; break;
 411                         case 3: y += 4; break;
 412                         case 4: y += 2; break;
 413                     }
 414                     if (y >= (img->h))
 415                     {
 416                         switch (++pass)
 417                         {
 418                             case 2: y = 4; break;
 419                             case 3: y = 2; break;
 420                             case 4: y = 1; break;
 421                         }
 422                     }
 423                 }
 424                 else
 425                 {
 426                     /* non-interlaced */
 427                     y++;
 428                 }
 429             }
 430         }
 431
 432         pos = 0;
 433         lastcode = readcode;
 434     }
 435     while (code != ab_fin);
 436
 437     return 0;
 438 }
 439
 440
 441 // CanRead:
 442 //  Returns TRUE if the file looks like a valid GIF, FALSE otherwise.
 443 //
 444 bool wxGIFDecoder::CanRead()
 445 {
 446     unsigned char buf[3];
 447     off_t pos;
 448
 449     pos = m_f->TellI();
 450     m_f->SeekI(0, wxFromStart);
 451     m_f->Read(buf, 3);
 452     m_f->SeekI(pos, wxFromStart);
 453
 454     return (memcmp(buf, "GIF", 3) == 0);
 455 }
 456
 457
 458 // ReadGIF:
 459 //  Reads and decodes one or more GIF images, depending on whether
 460 //  animated GIF support is enabled. Can read GIFs with any bit
 461 //  size (color depth), but the output images are always expanded
 462 //  to 8 bits per pixel. Also, the image palettes always contain
 463 //  256 colors, although some of them may be unused. Returns E_OK
 464 //  (== 0) on success, or an error code if something fails. Error
 465 //  codes are E_ARCHIVO, E_FORMATO, E_MEMORIA (see header file).
 466 //
 467 int wxGIFDecoder::ReadGIF()
 468 {
 469     int           ncolors, bits, interl, transparent, disposal, i;
 470     long          size;
 471     long          delay;
 472     unsigned char type;
 473     unsigned char pal[768];
 474     unsigned char buf[16];
 475     IMAGEN        **ppimg, *pimg, *pprev;
 476
 477     /* check GIF signature */
 478     if (!CanRead())
 479         return E_FORMATO;
 480
 481     /* check for and animated GIF support (ver. >= 89a) */
 482     m_f->SeekI(0, wxFromStart);
 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     while (1)
 513     {
 514         type = (unsigned char)m_f->GetC();
 515
 516         /* end of data? */
 517         if (type == 0x3B)
 518             break;
 519
 520         /* extension block? */
 521         if (type == 0x21)
 522         {
 523             if (((unsigned char)m_f->GetC()) == 0xF9)
 524             /* graphics control extension, parse it */
 525             {
 526                 m_f->Read(buf, 6);
 527
 528                 /* read delay and convert from 1/100 of a second to ms */
 529                 delay = 10 * (buf[2] + 256 * buf[3]);
 530
 531                 /* read transparent colour index, if used */
 532                 if (buf[1] & 0x01)
 533                     transparent = buf[4];
 534
 535                 /* read disposal method */
 536                 disposal = (buf[1] & 0x1C) - 1;
 537             }
 538             else
 539             /* other extension, skip */
 540             {
 541                 while ((i = (unsigned char)m_f->GetC()) != 0)
 542                 {
 543                     /* This line should not be neccessary!
 544                      * Some images are not loaded correctly
 545                      * without it. A bug in wxStream?
 546                      * Yes. Fixed now.
 547                      */
 548                     // m_f->SeekI(m_f->TellI(), wxFromStart);
 549
 550                     m_f->SeekI(i, wxFromCurrent);
 551                 }
 552             }
 553         }
 554
 555         /* image descriptor block? */
 556         if (type == 0x2C)
 557         {
 558             /* allocate memory for IMAGEN struct */
 559             pimg = (*ppimg) = (IMAGEN *) malloc(sizeof(IMAGEN));
 560
 561             if (pimg == NULL)
 562             {
 563                 Destroy();
 564                 return E_MEMORIA;
 565             }
 566
 567             /* fill in the data */
 568             m_f->Read(buf, 9);
 569             pimg->left = buf[4] + 256 * buf[5];
 570             pimg->top = buf[4] + 256 * buf[5];
 571             pimg->w = buf[4] + 256 * buf[5];
 572             pimg->h = buf[6] + 256 * buf[7];
 573             interl = ((buf[8] & 0x40)? 1 : 0);
 574             size = pimg->w * pimg->h;
 575
 576             pimg->transparent = transparent;
 577             pimg->disposal = disposal;
 578             pimg->delay = delay;
 579             pimg->next = NULL;
 580             pimg->prev = pprev;
 581             pprev = pimg;
 582             ppimg = &pimg->next;
 583
 584             /* allocate memory for image and palette */
 585             pimg->p   = (unsigned char *) malloc(size);
 586             pimg->pal = (unsigned char *) malloc(768);
 587
 588             if ((!pimg->p) || (!pimg->pal))
 589             {
 590                 Destroy();
 591                 return E_MEMORIA;
 592             }
 593
 594             /* load local color map if available, else use global map */
 595             if ((buf[8] & 0x80) == 0x80)
 596             {
 597                 ncolors = 2 << (buf[8] & 0x07);
 598                 m_f->Read(pimg->pal, 3 * ncolors);
 599             }
 600             else
 601                 memcpy(pimg->pal, pal, 768);
 602
 603             /* get initial code size from first byte in raster data */
 604             bits = (unsigned char)m_f->GetC();
 605
 606             /* decode image */
 607             dgif(pimg, interl, bits);
 608
 609             m_nimages++;
 610         }
 611
 612         /* if we have one image and no animated GIF support, exit */
 613         if (m_nimages == 1 && !m_anim)
 614             break;
 615     }
 616
 617     /* finish successfully :-) */
 618     if (m_nimages != 0)
 619     {
 620         m_image = 1;
 621         m_plast = pimg;
 622         m_pimage = m_pfirst;
 623     }
 624
 625     return E_OK;
 626 }
 627
 628 #endif // wxUSE_STREAMS && wxUSE_GIF