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:     3.02
   6 // Last rev:    1999/08/18
   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/setup.h"
  24 #endif
  25
  26 #if wxUSE_STREAMS
  27
  28 #include <stdlib.h>
  29 #include <string.h>
  30 #include "wx/defs.h"
  31 #include "wx/gifdecod.h"
  32
  33
  34 //---------------------------------------------------------------------------
  35 // wxGIFDecoder constructor and destructor
  36 //---------------------------------------------------------------------------
  37
  38 wxGIFDecoder::wxGIFDecoder(wxInputStream *s, bool anim)
  39 {
  40     m_f = s;
  41     m_anim = anim;
  42
  43     m_background = -1;
  44     m_screenw = 0;
  45     m_screenh = 0;
  46
  47     m_pimage  = NULL;
  48     m_pfirst  = NULL;
  49     m_plast   = NULL;
  50     m_image   = 0;
  51     m_nimages = 0;
  52 }
  53
  54 wxGIFDecoder::~wxGIFDecoder()
  55 {
  56     Destroy();
  57 }
  58
  59 void wxGIFDecoder::Destroy()
  60 {
  61     IMAGEN *pimg, *paux;
  62
  63     pimg = m_pfirst;
  64
  65     while (pimg != NULL)
  66     {
  67         paux = pimg->next;
  68         free(pimg->p);
  69         free(pimg->pal);
  70         free(pimg);
  71         pimg = paux;
  72     }
  73 }
  74
  75
  76 //---------------------------------------------------------------------------
  77 // Convert this image to a wxImage object
  78 //---------------------------------------------------------------------------
  79
  80 // This function was designed by Vaclav Slavik
  81
  82 bool wxGIFDecoder::ConvertToImage(wxImage *image) const
  83 {
  84     unsigned char *src, *dst, *pal;
  85     unsigned long i;
  86     int      transparent;
  87
  88     /* just in case... */
  89     image->Destroy();
  90
  91     /* create the image */
  92     image->Create(GetWidth(), GetHeight());
  93
  94     if (!image->Ok())
  95         return FALSE;
  96
  97     pal = GetPalette();
  98     src = GetData();
  99     dst = image->GetData();
 100     transparent = GetTransparentColour();
 101
 102     /* set transparent colour mask */
 103     if (transparent != -1)
 104     {
 105         for (i = 0; i < 256; i++)
 106         {
 107             if ((pal[3 * i + 0] == 255) &&
 108                 (pal[3 * i + 1] == 0) &&
 109                 (pal[3 * i + 2] == 255))
 110             {
 111                 pal[3 * i + 2] = 254;
 112             }
 113         }
 114
 115         pal[3 * transparent + 0] = 255,
 116         pal[3 * transparent + 1] = 0,
 117         pal[3 * transparent + 2] = 255;
 118
 119         image->SetMaskColour(255, 0, 255);
 120     }
 121     else
 122         image->SetMask(FALSE);
 123
 124     /* copy image data */
 125     for (i = 0; i < (GetWidth() * GetHeight()); i++, src++)
 126     {
 127         *(dst++) = pal[3 * (*src) + 0];
 128         *(dst++) = pal[3 * (*src) + 1];
 129         *(dst++) = pal[3 * (*src) + 2];
 130     }
 131
 132     return TRUE;
 133 }
 134
 135
 136 //---------------------------------------------------------------------------
 137 // Data accessors
 138 //---------------------------------------------------------------------------
 139
 140 // Get data for current frame
 141
 142 int wxGIFDecoder::GetFrameIndex() const         { return m_image; }
 143 unsigned char* wxGIFDecoder::GetData() const    { return (m_pimage->p); }
 144 unsigned char* wxGIFDecoder::GetPalette() const { return (m_pimage->pal); }
 145 unsigned int wxGIFDecoder::GetWidth() const     { return (m_pimage->w); }
 146 unsigned int wxGIFDecoder::GetHeight() const    { return (m_pimage->h); }
 147 unsigned int wxGIFDecoder::GetTop() const       { return (m_pimage->top); }
 148 unsigned int wxGIFDecoder::GetLeft() const      { return (m_pimage->left); }
 149 int wxGIFDecoder::GetTransparentColour() const  { return (m_pimage->transparent); }
 150 int wxGIFDecoder::GetDisposalMethod() const     { return (m_pimage->disposal); }
 151 long wxGIFDecoder::GetDelay() const             { return (m_pimage->delay); }
 152
 153 // Get global data
 154
 155 unsigned int wxGIFDecoder::GetLogicalScreenWidth() const    { return m_screenw; }
 156 unsigned int wxGIFDecoder::GetLogicalScreenHeight() const   { return m_screenh; }
 157 int wxGIFDecoder::GetBackgroundColour() const   { return m_background; }
 158 int wxGIFDecoder::GetNumberOfFrames() const     { return m_nimages; }
 159 bool wxGIFDecoder::IsAnimation() const          { return (m_nimages > 1); }
 160
 161
 162 //---------------------------------------------------------------------------
 163 // Functions to move through the animation
 164 //---------------------------------------------------------------------------
 165
 166 bool wxGIFDecoder::GoFirstFrame()
 167 {
 168     if (!IsAnimation())
 169         return FALSE;
 170
 171     m_image = 1;
 172     m_pimage = m_pfirst;
 173     return TRUE;
 174 }
 175
 176 bool wxGIFDecoder::GoLastFrame()
 177 {
 178     if (!IsAnimation())
 179         return FALSE;
 180
 181     m_image = m_nimages;
 182     m_pimage = m_plast;
 183     return TRUE;
 184 }
 185
 186 bool wxGIFDecoder::GoNextFrame(bool cyclic)
 187 {
 188     if (!IsAnimation())
 189         return FALSE;
 190
 191     if ((m_image < m_nimages) || (cyclic))
 192     {
 193         m_pimage = m_pimage->next;
 194         m_image++;
 195
 196         if (!m_pimage)
 197         {
 198             m_image = 1;
 199             m_pimage = m_pfirst;
 200         }
 201
 202         return TRUE;
 203     }
 204     else
 205         return FALSE;
 206 }
 207
 208 bool wxGIFDecoder::GoPrevFrame(bool cyclic)
 209 {
 210     if (!IsAnimation())
 211         return FALSE;
 212
 213     if ((m_image > 1) || (cyclic))
 214     {
 215         m_pimage = m_pimage->prev;
 216         m_image--;
 217
 218         if (!m_pimage)
 219         {
 220             m_image = m_nimages;
 221             m_pimage = m_plast;
 222         }
 223
 224         return TRUE;
 225     }
 226     else
 227         return FALSE;
 228 }
 229
 230 bool wxGIFDecoder::GoFrame(int which)
 231 {
 232     int i;
 233
 234     if (!IsAnimation())
 235         return FALSE;
 236
 237     if ((which >= 1) && (which <= m_nimages))
 238     {
 239         m_pimage = m_pfirst;
 240
 241         for (i = 1; i < which; i++)
 242             m_pimage = m_pimage->next;
 243
 244         return TRUE;
 245     }
 246     else
 247         return FALSE;
 248 }
 249
 250
 251 //---------------------------------------------------------------------------
 252 // GIF reading and decoding
 253 //---------------------------------------------------------------------------
 254
 255 // getcode:
 256 //  Reads the next code from the file stream, with size 'bits'
 257 //
 258 int wxGIFDecoder::getcode(int bits, int ab_fin)
 259 {
 260     unsigned int mask;          /* bit mask */
 261     unsigned int code;          /* code (result) */
 262
 263
 264     /* get remaining bits from last byte read */
 265     mask = (1 << bits) - 1;
 266     code = (m_lastbyte >> (8 - m_restbits)) & mask;
 267
 268     /* keep reading new bytes while needed */
 269     while (bits > m_restbits)
 270     {
 271         /* if no bytes left in this block, read the next block */
 272         if (m_restbyte == 0)
 273         {
 274             m_restbyte = (unsigned char)m_f->GetC();
 275
 276             /* Some encoders are a bit broken: instead of issuing
 277              * an end-of-image symbol (ab_fin) they come up with
 278              * a zero-length subblock!! We catch this here so
 279              * that the decoder sees an ab_fin code.
 280              */
 281             if (m_restbyte == 0)
 282             {
 283                 code = ab_fin;
 284                 break;
 285             }
 286         }
 287
 288         /* read next byte and isolate the bits we need */
 289         m_lastbyte = (unsigned char)m_f->GetC();
 290         mask       = (1 << (bits - m_restbits)) - 1;
 291         code       = code + ((m_lastbyte & mask) << m_restbits);
 292         m_restbyte--;
 293
 294         /* adjust total number of bits extracted from the buffer */
 295         m_restbits = m_restbits + 8;
 296     }
 297
 298     /* find number of bits remaining for next code */
 299     m_restbits = (m_restbits - bits);
 300
 301     return code;
 302 }
 303
 304
 305 // dgif:
 306 //  GIF decoding function. The initial code size (aka root size)
 307 //  is 'bits'. Supports interlaced images (interl == 1).
 308 //
 309 int wxGIFDecoder::dgif(IMAGEN *img, int interl, int bits)
 310 {
 311     int ab_prefix[4096];        /* alphabet (prefixes) */
 312     int ab_tail[4096];          /* alphabet (tails) */
 313     int stack[4096];            /* decompression stack */
 314
 315     int ab_clr;                 /* clear code */
 316     int ab_fin;                 /* end of info code */
 317     int ab_bits;                /* actual symbol width, in bits */
 318     int ab_free;                /* first free position in alphabet */
 319     int ab_max;                 /* last possible character in alphabet */
 320     int pass;                   /* pass number in interlaced images */
 321     int pos;                    /* index into decompresion stack */
 322     unsigned int x, y;          /* position in image buffer */
 323
 324     int code, readcode, lastcode, abcabca;
 325
 326     /* these won't change */
 327     ab_clr = (1 << bits);
 328     ab_fin = (1 << bits) + 1;
 329
 330     /* these will change through the decompression proccess */
 331     ab_bits  = bits + 1;
 332     ab_free  = (1 << bits) + 2;
 333     ab_max   = (1 << ab_bits) - 1;
 334     lastcode = -1;
 335     abcabca  = -1;
 336     pass     = 1;
 337     pos = x = y = 0;
 338
 339     /* reset static globals */
 340     m_restbits = 0;
 341     m_restbyte = 0;
 342     m_lastbyte = 0;
 343
 344     do
 345     {
 346         /* get next code */
 347         readcode = code = getcode(ab_bits, ab_fin);
 348
 349         /* end of image? */
 350         if (code == ab_fin) break;
 351
 352         /* reset alphabet? */
 353         if (code == ab_clr)
 354         {
 355             /* reset main variables */
 356             ab_bits  = bits + 1;
 357             ab_free  = (1 << bits) + 2;
 358             ab_max   = (1 << ab_bits) - 1;
 359             lastcode = -1;
 360             abcabca  = -1;
 361
 362             /* skip to next code */
 363             continue;
 364         }
 365
 366         /* unknown code: special case (like in ABCABCA) */
 367         if (code >= ab_free)
 368         {
 369             code = lastcode;            /* take last string */
 370             stack[pos++] = abcabca;     /* add first character */
 371         }
 372
 373         /* build the string for this code in the stack */
 374         while (code > ab_clr)
 375         {
 376             stack[pos++] = ab_tail[code];
 377             code         = ab_prefix[code];
 378         }
 379         stack[pos] = code;              /* push last code into the stack */
 380         abcabca    = code;              /* save for special case */
 381
 382         /* make new entry in alphabet (only if NOT just cleared) */
 383         if (lastcode != -1)
 384         {
 385             ab_prefix[ab_free] = lastcode;
 386             ab_tail[ab_free]   = code;
 387             ab_free++;
 388
 389             if ((ab_free > ab_max) && (ab_bits < 12))
 390             {
 391                 ab_bits++;
 392                 ab_max = (1 << ab_bits) - 1;
 393             }
 394         }
 395
 396         /* dump stack data to the buffer */
 397         while (pos >= 0)
 398         {
 399             (img->p)[x + (y * (img->w))] = (char)stack[pos--];
 400
 401             if (++x >= (img->w))
 402             {
 403                 x = 0;
 404
 405                 if (interl)
 406                 {
 407                     /* support for interlaced images */
 408                     switch (pass)
 409                     {
 410                         case 1: y += 8; break;
 411                         case 2: y += 8; break;
 412                         case 3: y += 4; break;
 413                         case 4: y += 2; break;
 414                     }
 415                     if (y >= (img->h))
 416                     {
 417                         switch (++pass)
 418                         {
 419                             case 2: y = 4; break;
 420                             case 3: y = 2; break;
 421                             case 4: y = 1; break;
 422                         }
 423                     }
 424                 }
 425                 else
 426                 {
 427                     /* non-interlaced */
 428                     y++;
 429                 }
 430             }
 431         }
 432
 433         pos = 0;
 434         lastcode = readcode;
 435     }
 436     while (code != ab_fin);
 437
 438     return 0;
 439 }
 440
 441
 442 // CanRead:
 443 //  Returns TRUE if the file looks like a valid GIF, FALSE otherwise.
 444 //
 445 bool wxGIFDecoder::CanRead()
 446 {
 447     unsigned char buf[3];
 448
 449     m_f->SeekI(0, wxFromStart);
 450     m_f->Read(buf, 3);
 451
 452     return (memcmp(buf, "GIF", 3) == 0);
 453 }
 454
 455
 456 // ReadGIF:
 457 //  Reads and decodes one or more GIF images, depending on whether
 458 //  animated GIF support is enabled. Can read GIFs with any bit
 459 //  size (color depth), but the output images are always expanded
 460 //  to 8 bits per pixel. Also, the image palettes always contain
 461 //  256 colors, although some of them may be unused. Returns E_OK
 462 //  (== 0) on success, or an error code if something fails. Error
 463 //  codes are E_ARCHIVO, E_FORMATO, E_MEMORIA (see header file).
 464 //
 465 int wxGIFDecoder::ReadGIF()
 466 {
 467     int           ncolors, bits, interl, transparent, disposal, i;
 468     long          size;
 469     long          delay;
 470     unsigned char type;
 471     unsigned char pal[768];
 472     unsigned char buf[16];
 473     IMAGEN        **ppimg, *pimg, *pprev;
 474
 475     /* check GIF signature */
 476     if (!CanRead())
 477         return E_FORMATO;
 478
 479     /* check for and animated GIF support (ver. >= 89a) */
 480     m_f->SeekI(0, wxFromStart);
 481     m_f->Read(buf, 6);
 482
 483     if (memcmp(buf + 3, "89a", 3) < 0)
 484         m_anim = FALSE;
 485
 486     /* read logical screen descriptor block (LSDB) */
 487     m_f->Read(buf, 7);
 488     m_screenw = buf[0] + 256 * buf[1];
 489     m_screenh = buf[2] + 256 * buf[3];
 490
 491     /* load global color map if available */
 492     if ((buf[4] & 0x80) == 0x80)
 493     {
 494         m_background = buf[5];
 495
 496         ncolors = 2 << (buf[4] & 0x07);
 497         m_f->Read(pal, 3 * ncolors);
 498     }
 499
 500     /* transparent colour, disposal method and delay default to unused */
 501     transparent = -1;
 502     disposal = -1;
 503     delay = -1;
 504
 505     /* read images */
 506     ppimg = &m_pfirst;
 507     pprev = NULL;
 508     pimg  = NULL;
 509
 510     while (1)
 511     {
 512         type = (unsigned char)m_f->GetC();
 513
 514         /* end of data? */
 515         if (type == 0x3B)
 516             break;
 517
 518         /* extension block? */
 519         if (type == 0x21)
 520         {
 521             if (((unsigned char)m_f->GetC()) == 0xF9)
 522             /* graphics control extension, parse it */
 523             {
 524                 m_f->Read(buf, 6);
 525
 526                 /* read delay and convert from 1/100 of a second to ms */
 527                 delay = 10 * (buf[2] + 256 * buf[3]);
 528
 529                 /* read transparent colour index, if used */
 530                 if (buf[1] & 0x01)
 531                     transparent = buf[4];
 532
 533                 /* read disposal method */
 534                 disposal = (buf[1] & 0x1C) - 1;
 535             }
 536             else
 537             /* other extension, skip */
 538             {
 539                 while ((i = (unsigned char)m_f->GetC()) != 0)
 540                 {
 541                     /* This line should not be neccessary!
 542                      * Some images are not loaded correctly
 543                      * without it. A bug in wxStream?
 544                      */
 545                     // m_f->SeekI(m_f->TellI(), wxFromStart);
 546                     m_f->SeekI(i, wxFromCurrent);
 547                 }
 548             }
 549         }
 550
 551         /* image descriptor block? */
 552         if (type == 0x2C)
 553         {
 554             /* allocate memory for IMAGEN struct */
 555             pimg = (*ppimg) = (IMAGEN *) malloc(sizeof(IMAGEN));
 556
 557             if (pimg == NULL)
 558             {
 559                 Destroy();
 560                 return E_MEMORIA;
 561             }
 562
 563             /* fill in the data */
 564             m_f->Read(buf, 9);
 565             pimg->left = buf[4] + 256 * buf[5];
 566             pimg->top = buf[4] + 256 * buf[5];
 567             pimg->w = buf[4] + 256 * buf[5];
 568             pimg->h = buf[6] + 256 * buf[7];
 569             interl = ((buf[8] & 0x40)? 1 : 0);
 570             size = pimg->w * pimg->h;
 571
 572             pimg->transparent = transparent;
 573             pimg->disposal = disposal;
 574             pimg->delay = delay;
 575             pimg->next = NULL;
 576             pimg->prev = pprev;
 577             pprev = pimg;
 578             ppimg = &pimg->next;
 579
 580             /* allocate memory for image and palette */
 581             pimg->p   = (unsigned char *) malloc(size);
 582             pimg->pal = (unsigned char *) malloc(768);
 583
 584             if ((!pimg->p) || (!pimg->pal))
 585             {
 586                 Destroy();
 587                 return E_MEMORIA;
 588             }
 589
 590             /* load local color map if available, else use global map */
 591             if ((buf[8] & 0x80) == 0x80)
 592             {
 593                 ncolors = 2 << (buf[8] & 0x07);
 594                 m_f->Read(pimg->pal, 3 * ncolors);
 595             }
 596             else
 597                 memcpy(pimg->pal, pal, 768);
 598
 599             /* get initial code size from first byte in raster data */
 600             bits = (unsigned char)m_f->GetC();
 601
 602             /* decode image */
 603             dgif(pimg, interl, bits);
 604
 605             m_nimages++;
 606         }
 607
 608         /* if we have one image and no animated GIF support, exit */
 609         if (m_nimages == 1 && !m_anim)
 610             break;
 611     }
 612
 613     /* finish successfully :-) */
 614     if (m_nimages != 0)
 615     {
 616         m_image = 1;
 617         m_plast = pimg;
 618         m_pimage = m_pfirst;
 619     }
 620
 621     return E_OK;
 622 }
 623
 624 #endif // wxUSE_STREAM