src/common/imaggif.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        imaggif.cpp
   3 // Purpose:     wxGIFHandler
   4 // Author:      Guillermo Rodriguez Garcia
   5 //              wxWindows adaptation by Vaclav Slavik
   6 // Licence:     wxWindows licence
   7 /////////////////////////////////////////////////////////////////////////////
   8
   9 #ifdef __GNUG__
  10 #pragma implementation "imaggif.h"
  11 #endif
  12
  13 // For compilers that support precompilation, includes "wx.h".
  14 #include <wx/wxprec.h>
  15
  16 #ifdef __BORLANDC__
  17 #pragma hdrstop
  18 #endif
  19
  20 #include <wx/wx.h>
  21
  22 #include <wx/image.h>
  23 #include <wx/wfstream.h>
  24 #include <wx/module.h>
  25
  26 #include <wx/imaggif.h>
  27
  28 /*
  29
  30 FOLLOWING CODE IS BY G.R.G. :
  31 (except wxInputStream stuff)
  32
  33 */
  34
  35 /************************************************************************
  36   READGIF.H - Reads a GIF file
  37  ------------------------------------------------------------------------
  38   Guillermo Rodriguez Garcia
  39   <guille@iies.es>
  40
  41   Version: 2.1
  42 *************************************************************************/
  43
  44
  45 typedef struct
  46 {
  47     int w;                  /* width */
  48     int h;                  /* height */
  49     int transparent;        /* transparent color (-1 = none) */
  50     unsigned char *p;       /* bitmap */
  51     unsigned char *pal;     /* palette */
  52 } IMAGEN;
  53
  54
  55
  56 /************************************************************************
  57   READGIF.C - Reads a GIF file
  58  ------------------------------------------------------------------------
  59   Guillermo Rodriguez Garcia
  60   <guille@iies.es>
  61
  62   Version: 2.1
  63 *************************************************************************/
  64
  65
  66 #include <stdlib.h>
  67 #include <string.h>
  68
  69
  70 /* error codes */
  71 #define E_OK        0               /* everything was OK */
  72 #define E_ARCHIVO   -1              /* error opening file */
  73 #define E_FORMATO   -2              /* error in gif header */
  74 #define E_MEMORIA   -3              /* error allocating memory */
  75
  76
  77 /* This class binding is by VS, so all bugs in it are mine ;-) */
  78
  79 class gifDecoder
  80 {
  81     private:
  82         /* globals */
  83         int            restbits;            /* remaining valid bits */
  84         unsigned int   restbyte;            /* remaining bytes in this block */
  85         unsigned int   lastbyte;            /* last byte read */
  86
  87         wxInputStream  *f;                  /* input file */
  88
  89         public:
  90                 gifDecoder(wxInputStream *s) { f = s; }
  91                 int getcode(int bits);
  92                 int dgif(IMAGEN *img, int interl, int bits);
  93                 int readgif(IMAGEN *img);
  94 };
  95
  96
  97
  98 /* getcode:
  99  *  Reads the next code from the file, with size 'bits'
 100  */
 101 int gifDecoder::getcode(int bits)
 102 {
 103     unsigned int    mask;           /* bit mask */
 104     unsigned int    code;           /* code (result) */
 105
 106
 107     /* get remaining bits from last byte read */
 108     mask = (1 << bits) - 1;
 109     code = (lastbyte >> (8 - restbits)) & mask;
 110
 111     /* keep reading new bytes while needed */
 112     while (bits > restbits)
 113     {
 114         /* if no bytes left in this block, read the next block */
 115         if (restbyte == 0)
 116             restbyte = (unsigned char)f->GetC();
 117
 118         /* read next byte and isolate the bits we need */
 119         lastbyte = (unsigned char)f->GetC();
 120         mask     = (1 << (bits - restbits)) - 1;
 121         code     = code + ((lastbyte & mask) << restbits);
 122         restbyte--;
 123
 124         /* adjust total number of bits extracted from the buffer */
 125         restbits = restbits + 8;
 126     }
 127
 128     /* find number of bits reamining for next code */
 129     restbits = (restbits - bits);
 130
 131     return code;
 132 }
 133
 134
 135
 136 /* dgif:
 137  *  GIF decoding function. The initial code size (aka root size)
 138  *  is 'bits'. Supports interlaced images (interl == 1).
 139  */
 140 int gifDecoder::dgif(IMAGEN *img, int interl, int bits)
 141 {
 142     int ab_prefix[4096];        /* alphabet (prefixes) */
 143     int ab_tail[4096];          /* alphabet (tails) */
 144     int stack[4096];            /* decompression stack */
 145
 146     int ab_clr;                 /* clear code */
 147     int ab_fin;                 /* end of info code */
 148     int ab_bits;                /* actual symbol width, in bits */
 149     int ab_free;                /* first free position in alphabet */
 150     int ab_max;                 /* last possible character in alphabet */
 151     int pass;                   /* pass number in interlaced images */
 152     int pos;                    /* index into decompresion stack */
 153     int x, y;                   /* position in image buffer */
 154
 155     int code, readcode, lastcode, abcabca;
 156
 157     /* these won't change */
 158     ab_clr  = (1 << bits);
 159     ab_fin  = (1 << bits) + 1;
 160
 161     /* these will change through the decompression proccess */
 162     ab_bits  = bits + 1;
 163     ab_free  = (1 << bits) + 2;
 164     ab_max   = (1 << ab_bits) - 1;
 165     lastcode = -1;
 166     abcabca  = -1;
 167     pass     = 1;
 168     pos = x = y = 0;
 169
 170     /* reset static globals */
 171     restbits = 0;
 172     restbyte = 0;
 173     lastbyte = 0;
 174
 175     do
 176     {
 177         /* get next code */
 178         readcode = code = getcode(ab_bits);
 179
 180         /* end of image? */
 181         if (code == ab_fin) break;
 182
 183         /* reset alphabet? */
 184         if (code == ab_clr)
 185         {
 186             /* reset main variables */
 187             ab_bits  = bits + 1;
 188             ab_free  = (1 << bits) + 2;
 189             ab_max   = (1 << ab_bits) - 1;
 190             lastcode = -1;
 191             abcabca  = -1;
 192
 193             /* skip to next code */
 194             continue;
 195         }
 196
 197         /* unknown code: special case (like in ABCABCA) */
 198         if (code >= ab_free)
 199         {
 200             code = lastcode;            /* take last string */
 201             stack[pos++] = abcabca;     /* add first character */
 202         }
 203
 204         /* build the string for this code in the stack */
 205         while (code > ab_clr)
 206         {
 207             stack[pos++] = ab_tail[code];
 208             code         = ab_prefix[code];
 209         }
 210         stack[pos] = code;              /* push last code into the stack */
 211         abcabca    = code;              /* save for special case */
 212
 213         /* make new entry in alphabet (only if NOT just cleared) */
 214         if (lastcode != -1)
 215         {
 216             ab_prefix[ab_free] = lastcode;
 217             ab_tail[ab_free]   = code;
 218             ab_free++;
 219
 220             if ((ab_free > ab_max) && (ab_bits < 12))
 221             {
 222                 ab_bits++;
 223                 ab_max = (1 << ab_bits) - 1;
 224             }
 225         }
 226
 227         /* dump stack data to the buffer */
 228         while (pos >= 0)
 229         {
 230             (img->p)[x + (y * (img->w))] = (char)stack[pos--];
 231
 232             if (++x >= (img->w))
 233             {
 234                 x = 0;
 235
 236                 if (interl)
 237                 {
 238                     /* support for interlaced images */
 239                     switch (pass)
 240                     {
 241                         case 1: y += 8; break;
 242                         case 2: y += 8; break;
 243                         case 3: y += 4; break;
 244                         case 4: y += 2; break;
 245                     }
 246                     if (y >= (img->h))
 247                     {
 248                         switch (++pass)
 249                         {
 250                             case 2: y = 4; break;
 251                             case 3: y = 2; break;
 252                             case 4: y = 1; break;
 253                         }
 254                     }
 255                 }
 256                 else
 257                 {
 258                     /* non-interlaced */
 259                     y++;
 260                 }
 261             }
 262         }
 263
 264         pos = 0;
 265         lastcode = readcode;
 266     }
 267     while (code != ab_fin);
 268
 269     return 0;
 270 }
 271
 272
 273
 274 /* readgif:
 275  *  Reads a GIF image from the file with filename 'nombre' in the
 276  *  IMAGEN structure pointed by 'img'. Can read GIFs with any bit
 277  *  size (color depth), but the output image is always expanded
 278  *  to 8 bits per pixel. Also, the image palette always contains
 279  *  256 colors, although some of them may be unused. Returns E_OK
 280  *  (== 0) on success, or an error code if something fails. Error
 281  *  codes are E_ARCHIVO, E_FORMATO, E_MEMORIA (see above).
 282  */
 283 int gifDecoder::readgif(IMAGEN *img)
 284 {
 285     int             size, ncolors, bits, interl, i;
 286     unsigned char   pal[768];
 287     unsigned char   buf[16];
 288
 289
 290     /* read header and logical screen descriptor block (LSDB) */
 291     f->Read(buf, 13);
 292
 293     /* check GIF signature */
 294     if (memcmp(buf, "GIF", 3) != 0) return E_FORMATO;
 295
 296     /* load global color map if available */
 297     if ((buf[10] & 0x80) == 0x80)
 298     {
 299         ncolors = 2 << (buf[10] & 0x07);
 300         f->Read(pal, 3 * ncolors);
 301     }
 302
 303     /* assume no transparent color */
 304     img->transparent = -1;
 305
 306     /* skip most extensions */
 307     while (((unsigned char)f->GetC()) == 0x21)               /* separator */
 308     {
 309         if (((unsigned char)f->GetC()) == 0xF9)              /* graphic control ext. */
 310         {
 311             f->Read(buf, 6);
 312             if (buf[1] & 0x01)
 313                 img->transparent = buf[4];
 314         }
 315         else
 316             while ((i = (unsigned char)f->GetC()) != 0)    /* byte count */
 317                 f->SeekI(i, wxFromCurrent);
 318     }
 319
 320     /* read image descriptor block (IDB) */
 321     f->Read(buf, 9);
 322     img->w = buf[4] + 256 * buf[5];
 323     img->h = buf[6] + 256 * buf[7];
 324     size   = img->w * img->h;
 325     interl = ((buf[8] & 0x40)? 1 : 0);
 326
 327     /* load local color map if available */
 328     if ((buf[8] & 0x80) == 0x80)
 329     {
 330         ncolors = 2 << (buf[8] & 0x07);
 331         f->Read(pal, 3 * ncolors);
 332     }
 333
 334     /* get initial code size from first byte in raster data */
 335     bits = (unsigned char)f->GetC();
 336
 337     /* allocate memory for image and palette */
 338     if ((img->p   = (unsigned char*) malloc(size)) == NULL) return E_MEMORIA;
 339     if ((img->pal = (unsigned char*) malloc(768))  == NULL) return E_MEMORIA;
 340
 341     /* shift palette to fit VGA 6-bit format */
 342     for (i = 0; i < 768; i++)
 343         (img->pal)[i] = (unsigned char)pal[i]; /* >> 2 not in wxWin */
 344
 345     /* decode GIF */
 346     dgif(img, interl, bits);
 347
 348     /* finish successfully :-) */
 349     return E_OK;
 350 }
 351
 352
 353
 354 /*
 355
 356 FOLLOWING CODE IS BY V.S. :
 357
 358 */
 359
 360 //-----------------------------------------------------------------------------
 361 // wxGIFHandler
 362 //-----------------------------------------------------------------------------
 363
 364 IMPLEMENT_DYNAMIC_CLASS(wxGIFHandler,wxImageHandler)
 365
 366 bool wxGIFHandler::LoadFile( wxImage *image, wxInputStream& stream )
 367 {
 368     unsigned char *ptr, *src, *pal;
 369     IMAGEN igif;
 370     int i;
 371     gifDecoder *decod;
 372
 373     image->Destroy();
 374
 375     decod = new gifDecoder(&stream);
 376
 377     if (decod->readgif(&igif) != E_OK) {
 378         wxLogDebug(_T("Error reading GIF"));
 379         delete decod;
 380         return FALSE;
 381     }
 382     delete decod;
 383
 384     image->Create(igif.w, igif.h);
 385     if (!image->Ok()) {
 386         free(igif.pal);
 387         free(igif.p);
 388         return FALSE;
 389     }
 390
 391     ptr = image->GetData();
 392     src = igif.p;
 393     pal = igif.pal;
 394
 395     if (igif.transparent != -1) {
 396         for (i = 0; i < 256; i++)
 397             if ((pal[3 * i + 0] == 255) && (pal[3 * i + 1] == 0) && (pal[3 * i + 2] == 255)) pal[3 * i + 2] = 254;
 398         pal[3 * (igif.transparent) + 0] = 255,
 399         pal[3 * (igif.transparent) + 1] = 0,
 400         pal[3 * (igif.transparent) + 2] = 255;
 401         image->SetMaskColour(255, 0, 255);
 402     }
 403     else image->SetMask(FALSE);
 404
 405     for (i = 0; i < igif.w * igif.h; i++, src++) {
 406         *(ptr++) = pal[3 * (*src) + 0];
 407         *(ptr++) = pal[3 * (*src) + 1];
 408         *(ptr++) = pal[3 * (*src) + 2];
 409     }
 410
 411     free(igif.pal);
 412     free(igif.p);
 413     return TRUE;
 414 }
 415
 416 bool wxGIFHandler::SaveFile( wxImage * WXUNUSED(image),
 417                              wxOutputStream& WXUNUSED(stream) )
 418 {
 419     wxLogDebug(_T("wxGIFHandler is read-only!!"));
 420     return FALSE;
 421 }
 422
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