src/common/imagtiff.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/common/imagtiff.cpp
   3 // Purpose:     wxImage TIFF handler
   4 // Author:      Robert Roebling
   5 // RCS-ID:      $Id$
   6 // Copyright:   (c) Robert Roebling
   7 // Licence:     wxWindows licence
   8 /////////////////////////////////////////////////////////////////////////////
   9
  10 // ============================================================================
  11 // declarations
  12 // ============================================================================
  13
  14 // ----------------------------------------------------------------------------
  15 // headers
  16 // ----------------------------------------------------------------------------
  17
  18 // For compilers that support precompilation, includes "wx.h".
  19 #include "wx/wxprec.h"
  20
  21 #ifdef __BORLANDC__
  22     #pragma hdrstop
  23 #endif
  24
  25 #if wxUSE_IMAGE && wxUSE_LIBTIFF
  26
  27 #include "wx/imagtiff.h"
  28 #include "wx/versioninfo.h"
  29
  30 #ifndef WX_PRECOMP
  31     #include "wx/log.h"
  32     #include "wx/app.h"
  33     #include "wx/intl.h"
  34     #include "wx/bitmap.h"
  35     #include "wx/module.h"
  36     #include "wx/wxcrtvararg.h"
  37 #endif
  38
  39 extern "C"
  40 {
  41 #ifdef __DMC__
  42     #include "tif_config.h"
  43 #endif
  44     #include "tiff.h"
  45     #include "tiffio.h"
  46 }
  47 #include "wx/filefn.h"
  48 #include "wx/wfstream.h"
  49
  50 #ifndef TIFFLINKAGEMODE
  51     #if defined(__WATCOMC__) && defined(__WXMGL__)
  52         #define TIFFLINKAGEMODE cdecl
  53     #else
  54         #define TIFFLINKAGEMODE LINKAGEMODE
  55     #endif
  56 #endif
  57
  58 // ============================================================================
  59 // implementation
  60 // ============================================================================
  61
  62 // ----------------------------------------------------------------------------
  63 // TIFF library error/warning handlers
  64 // ----------------------------------------------------------------------------
  65
  66 static wxString
  67 FormatTiffMessage(const char *module, const char *fmt, va_list ap)
  68 {
  69     char buf[512];
  70     if ( wxCRT_VsnprintfA(buf, WXSIZEOF(buf), fmt, ap) <= 0 )
  71     {
  72         // this isn't supposed to happen, but if it does, it's better
  73         // than nothing
  74         strcpy(buf, "Incorrectly formatted TIFF message");
  75     }
  76     buf[WXSIZEOF(buf)-1] = 0; // make sure it is always NULL-terminated
  77
  78     wxString msg(buf);
  79     if ( module )
  80         msg += wxString::Format(_(" (in module \"%s\")"), module);
  81
  82     return msg;
  83 }
  84
  85 extern "C"
  86 {
  87
  88 static void
  89 TIFFwxWarningHandler(const char* module, const char *fmt, va_list ap)
  90 {
  91     wxLogWarning("%s", FormatTiffMessage(module, fmt, ap));
  92 }
  93
  94 static void
  95 TIFFwxErrorHandler(const char* module, const char *fmt, va_list ap)
  96 {
  97     wxLogError("%s", FormatTiffMessage(module, fmt, ap));
  98 }
  99
 100 } // extern "C"
 101
 102 //-----------------------------------------------------------------------------
 103 // wxTIFFHandler
 104 //-----------------------------------------------------------------------------
 105
 106 IMPLEMENT_DYNAMIC_CLASS(wxTIFFHandler,wxImageHandler)
 107
 108 wxTIFFHandler::wxTIFFHandler()
 109 {
 110     m_name = wxT("TIFF file");
 111     m_extension = wxT("tif");
 112     m_altExtensions.Add(wxT("tiff"));
 113     m_type = wxBITMAP_TYPE_TIF;
 114     m_mime = wxT("image/tiff");
 115     TIFFSetWarningHandler((TIFFErrorHandler) TIFFwxWarningHandler);
 116     TIFFSetErrorHandler((TIFFErrorHandler) TIFFwxErrorHandler);
 117 }
 118
 119 #if wxUSE_STREAMS
 120
 121 // helper to translate our, possibly 64 bit, wxFileOffset to TIFF, always 32
 122 // bit, toff_t
 123 static toff_t wxFileOffsetToTIFF(wxFileOffset ofs)
 124 {
 125     if ( ofs == wxInvalidOffset )
 126         return (toff_t)-1;
 127
 128     toff_t tofs = wx_truncate_cast(toff_t, ofs);
 129     wxCHECK_MSG( (wxFileOffset)tofs == ofs, (toff_t)-1,
 130                     wxT("TIFF library doesn't support large files") );
 131
 132     return tofs;
 133 }
 134
 135 // another helper to convert standard seek mode to our
 136 static wxSeekMode wxSeekModeFromTIFF(int whence)
 137 {
 138     switch ( whence )
 139     {
 140         case SEEK_SET:
 141             return wxFromStart;
 142
 143         case SEEK_CUR:
 144             return wxFromCurrent;
 145
 146         case SEEK_END:
 147             return wxFromEnd;
 148
 149         default:
 150             return wxFromCurrent;
 151     }
 152 }
 153
 154 extern "C"
 155 {
 156
 157 tsize_t TIFFLINKAGEMODE
 158 wxTIFFNullProc(thandle_t WXUNUSED(handle),
 159           tdata_t WXUNUSED(buf),
 160           tsize_t WXUNUSED(size))
 161 {
 162     return (tsize_t) -1;
 163 }
 164
 165 tsize_t TIFFLINKAGEMODE
 166 wxTIFFReadProc(thandle_t handle, tdata_t buf, tsize_t size)
 167 {
 168     wxInputStream *stream = (wxInputStream*) handle;
 169     stream->Read( (void*) buf, (size_t) size );
 170     return wx_truncate_cast(tsize_t, stream->LastRead());
 171 }
 172
 173 tsize_t TIFFLINKAGEMODE
 174 wxTIFFWriteProc(thandle_t handle, tdata_t buf, tsize_t size)
 175 {
 176     wxOutputStream *stream = (wxOutputStream*) handle;
 177     stream->Write( (void*) buf, (size_t) size );
 178     return wx_truncate_cast(tsize_t, stream->LastWrite());
 179 }
 180
 181 toff_t TIFFLINKAGEMODE
 182 wxTIFFSeekIProc(thandle_t handle, toff_t off, int whence)
 183 {
 184     wxInputStream *stream = (wxInputStream*) handle;
 185
 186     return wxFileOffsetToTIFF(stream->SeekI((wxFileOffset)off,
 187                                             wxSeekModeFromTIFF(whence)));
 188 }
 189
 190 toff_t TIFFLINKAGEMODE
 191 wxTIFFSeekOProc(thandle_t handle, toff_t off, int whence)
 192 {
 193     wxOutputStream *stream = (wxOutputStream*) handle;
 194
 195     toff_t offset = wxFileOffsetToTIFF(
 196         stream->SeekO((wxFileOffset)off, wxSeekModeFromTIFF(whence)) );
 197
 198     if (offset != (toff_t) -1 || whence != SEEK_SET)
 199     {
 200         return offset;
 201     }
 202
 203
 204     /*
 205     Try to workaround problems with libtiff seeking past the end of streams.
 206
 207     This occurs when libtiff is writing tag entries past the end of a
 208     stream but hasn't written the directory yet (which will be placed
 209     before the tags and contain offsets to the just written tags).
 210     The behaviour for seeking past the end of a stream is not consistent
 211     and doesn't work with for example wxMemoryOutputStream. When this type
 212     of seeking fails (with SEEK_SET), fill in the gap with zeroes and try
 213     again.
 214     */
 215
 216     wxFileOffset streamLength = stream->GetLength();
 217     if (streamLength != wxInvalidOffset && (wxFileOffset) off > streamLength)
 218     {
 219        if (stream->SeekO(streamLength, wxFromStart) == wxInvalidOffset)
 220        {
 221            return (toff_t) -1;
 222        }
 223
 224        for (wxFileOffset i = 0; i < (wxFileOffset) off - streamLength; ++i)
 225        {
 226            stream->PutC(0);
 227        }
 228     }
 229
 230     return wxFileOffsetToTIFF( stream->TellO() );
 231 }
 232
 233 int TIFFLINKAGEMODE
 234 wxTIFFCloseIProc(thandle_t WXUNUSED(handle))
 235 {
 236     // there is no need to close the input stream
 237     return 0;
 238 }
 239
 240 int TIFFLINKAGEMODE
 241 wxTIFFCloseOProc(thandle_t handle)
 242 {
 243     wxOutputStream *stream = (wxOutputStream*) handle;
 244
 245     return stream->Close() ? 0 : -1;
 246 }
 247
 248 toff_t TIFFLINKAGEMODE
 249 wxTIFFSizeProc(thandle_t handle)
 250 {
 251     wxStreamBase *stream = (wxStreamBase*) handle;
 252     return (toff_t) stream->GetSize();
 253 }
 254
 255 int TIFFLINKAGEMODE
 256 wxTIFFMapProc(thandle_t WXUNUSED(handle),
 257              tdata_t* WXUNUSED(pbase),
 258              toff_t* WXUNUSED(psize))
 259 {
 260     return 0;
 261 }
 262
 263 void TIFFLINKAGEMODE
 264 wxTIFFUnmapProc(thandle_t WXUNUSED(handle),
 265                tdata_t WXUNUSED(base),
 266                toff_t WXUNUSED(size))
 267 {
 268 }
 269
 270 } // extern "C"
 271
 272 TIFF*
 273 TIFFwxOpen(wxInputStream &stream, const char* name, const char* mode)
 274 {
 275     TIFF* tif = TIFFClientOpen(name, mode,
 276         (thandle_t) &stream,
 277         wxTIFFReadProc, wxTIFFNullProc,
 278         wxTIFFSeekIProc, wxTIFFCloseIProc, wxTIFFSizeProc,
 279         wxTIFFMapProc, wxTIFFUnmapProc);
 280
 281     return tif;
 282 }
 283
 284 TIFF*
 285 TIFFwxOpen(wxOutputStream &stream, const char* name, const char* mode)
 286 {
 287     TIFF* tif = TIFFClientOpen(name, mode,
 288         (thandle_t) &stream,
 289         wxTIFFNullProc, wxTIFFWriteProc,
 290         wxTIFFSeekOProc, wxTIFFCloseOProc, wxTIFFSizeProc,
 291         wxTIFFMapProc, wxTIFFUnmapProc);
 292
 293     return tif;
 294 }
 295
 296 bool wxTIFFHandler::LoadFile( wxImage *image, wxInputStream& stream, bool verbose, int index )
 297 {
 298     if (index == -1)
 299         index = 0;
 300
 301     image->Destroy();
 302
 303     TIFF *tif = TIFFwxOpen( stream, "image", "r" );
 304
 305     if (!tif)
 306     {
 307         if (verbose)
 308         {
 309             wxLogError( _("TIFF: Error loading image.") );
 310         }
 311
 312         return false;
 313     }
 314
 315     if (!TIFFSetDirectory( tif, (tdir_t)index ))
 316     {
 317         if (verbose)
 318         {
 319             wxLogError( _("Invalid TIFF image index.") );
 320         }
 321
 322         TIFFClose( tif );
 323
 324         return false;
 325     }
 326
 327     uint32 w, h;
 328     uint32 *raster;
 329
 330     TIFFGetField( tif, TIFFTAG_IMAGEWIDTH, &w );
 331     TIFFGetField( tif, TIFFTAG_IMAGELENGTH, &h );
 332
 333     uint16 photometric;
 334     uint16 samplesPerPixel;
 335     uint16 extraSamples;
 336     uint16* samplesInfo;
 337     TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &samplesPerPixel);
 338     TIFFGetFieldDefaulted(tif, TIFFTAG_EXTRASAMPLES,
 339                           &extraSamples, &samplesInfo);
 340     if (!TIFFGetField(tif, TIFFTAG_PHOTOMETRIC, &photometric))
 341     {
 342         photometric = PHOTOMETRIC_MINISWHITE;
 343     }
 344     const bool hasAlpha = (extraSamples >= 1
 345         && ((samplesInfo[0] == EXTRASAMPLE_UNSPECIFIED && samplesPerPixel > 3)
 346             || samplesInfo[0] == EXTRASAMPLE_ASSOCALPHA
 347             || samplesInfo[0] == EXTRASAMPLE_UNASSALPHA))
 348         || (extraSamples == 0 && samplesPerPixel == 4
 349             && photometric == PHOTOMETRIC_RGB);
 350
 351     // guard against integer overflow during multiplication which could result
 352     // in allocating a too small buffer and then overflowing it
 353     const double bytesNeeded = (double)w * (double)h * sizeof(uint32);
 354     if ( bytesNeeded >= wxUINT32_MAX )
 355     {
 356         if ( verbose )
 357         {
 358             wxLogError( _("TIFF: Image size is abnormally big.") );
 359         }
 360
 361         TIFFClose(tif);
 362
 363         return false;
 364     }
 365
 366     raster = (uint32*) _TIFFmalloc( (uint32)bytesNeeded );
 367
 368     if (!raster)
 369     {
 370         if (verbose)
 371         {
 372             wxLogError( _("TIFF: Couldn't allocate memory.") );
 373         }
 374
 375         TIFFClose( tif );
 376
 377         return false;
 378     }
 379
 380     image->Create( (int)w, (int)h );
 381     if (!image->IsOk())
 382     {
 383         if (verbose)
 384         {
 385             wxLogError( _("TIFF: Couldn't allocate memory.") );
 386         }
 387
 388         _TIFFfree( raster );
 389         TIFFClose( tif );
 390
 391         return false;
 392     }
 393
 394     if ( hasAlpha )
 395         image->SetAlpha();
 396
 397     if (!TIFFReadRGBAImage( tif, w, h, raster, 0 ))
 398     {
 399         if (verbose)
 400         {
 401             wxLogError( _("TIFF: Error reading image.") );
 402         }
 403
 404         _TIFFfree( raster );
 405         image->Destroy();
 406         TIFFClose( tif );
 407
 408         return false;
 409     }
 410
 411     unsigned char *ptr = image->GetData();
 412     ptr += w*3*(h-1);
 413
 414     unsigned char *alpha = hasAlpha ? image->GetAlpha() : NULL;
 415     if ( hasAlpha )
 416         alpha += w*(h-1);
 417
 418     uint32 pos = 0;
 419
 420     for (uint32 i = 0; i < h; i++)
 421     {
 422         for (uint32 j = 0; j < w; j++)
 423         {
 424             *(ptr++) = (unsigned char)TIFFGetR(raster[pos]);
 425             *(ptr++) = (unsigned char)TIFFGetG(raster[pos]);
 426             *(ptr++) = (unsigned char)TIFFGetB(raster[pos]);
 427             if ( hasAlpha )
 428                 *(alpha++) = (unsigned char)TIFFGetA(raster[pos]);
 429
 430             pos++;
 431         }
 432
 433         // subtract line we just added plus one line:
 434         ptr -= 2*w*3;
 435         if ( hasAlpha )
 436             alpha -= 2*w;
 437     }
 438
 439
 440     uint16 spp, bpp, compression;
 441     /*
 442     Read some baseline TIFF tags which helps when re-saving a TIFF
 443     to be similar to the original image.
 444     */
 445     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &spp) )
 446     {
 447         image->SetOption(wxIMAGE_OPTION_SAMPLESPERPIXEL, spp);
 448     }
 449
 450     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_BITSPERSAMPLE, &bpp) )
 451     {
 452         image->SetOption(wxIMAGE_OPTION_BITSPERSAMPLE, bpp);
 453     }
 454
 455     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_COMPRESSION, &compression) )
 456     {
 457         image->SetOption(wxIMAGE_OPTION_COMPRESSION, compression);
 458     }
 459
 460     // Set the resolution unit.
 461     wxImageResolution resUnit = wxIMAGE_RESOLUTION_NONE;
 462     uint16 tiffRes;
 463     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_RESOLUTIONUNIT, &tiffRes) )
 464     {
 465         switch (tiffRes)
 466         {
 467             default:
 468                 wxLogWarning(_("Unknown TIFF resolution unit %d ignored"),
 469                     tiffRes);
 470                 // fall through
 471
 472             case RESUNIT_NONE:
 473                 resUnit = wxIMAGE_RESOLUTION_NONE;
 474                 break;
 475
 476             case RESUNIT_INCH:
 477                 resUnit = wxIMAGE_RESOLUTION_INCHES;
 478                 break;
 479
 480             case RESUNIT_CENTIMETER:
 481                 resUnit = wxIMAGE_RESOLUTION_CM;
 482                 break;
 483         }
 484     }
 485
 486     image->SetOption(wxIMAGE_OPTION_RESOLUTIONUNIT, resUnit);
 487
 488     /*
 489     Set the image resolution if it's available. Resolution tag is not
 490     dependant on RESOLUTIONUNIT != RESUNIT_NONE (according to TIFF spec).
 491     */
 492     float resX, resY;
 493
 494     if ( TIFFGetField(tif, TIFFTAG_XRESOLUTION, &resX) )
 495     {
 496         /*
 497         Use a string value to not lose precision.
 498         rounding to int as cm and then converting to inch may
 499         result in whole integer rounding error, eg. 201 instead of 200 dpi.
 500         If an app wants an int, GetOptionInt will convert and round down.
 501         */
 502         image->SetOption(wxIMAGE_OPTION_RESOLUTIONX,
 503             wxString::FromCDouble((double) resX));
 504     }
 505
 506     if ( TIFFGetField(tif, TIFFTAG_YRESOLUTION, &resY) )
 507     {
 508         image->SetOption(wxIMAGE_OPTION_RESOLUTIONY,
 509             wxString::FromCDouble((double) resY));
 510     }
 511
 512     _TIFFfree( raster );
 513
 514     TIFFClose( tif );
 515
 516     return true;
 517 }
 518
 519 int wxTIFFHandler::DoGetImageCount( wxInputStream& stream )
 520 {
 521     TIFF *tif = TIFFwxOpen( stream, "image", "r" );
 522
 523     if (!tif)
 524         return 0;
 525
 526     int dircount = 0;  // according to the libtiff docs, dircount should be set to 1 here???
 527     do {
 528         dircount++;
 529     } while (TIFFReadDirectory(tif));
 530
 531     TIFFClose( tif );
 532
 533     // NOTE: this function modifies the current stream position but it's ok
 534     //       (see wxImageHandler::GetImageCount)
 535
 536     return dircount;
 537 }
 538
 539 bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 540 {
 541     TIFF *tif = TIFFwxOpen( stream, "image", "w" );
 542
 543     if (!tif)
 544     {
 545         if (verbose)
 546         {
 547             wxLogError( _("TIFF: Error saving image.") );
 548         }
 549
 550         return false;
 551     }
 552
 553     TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
 554     TIFFSetField(tif, TIFFTAG_IMAGEWIDTH,  (uint32)image->GetWidth());
 555     TIFFSetField(tif, TIFFTAG_IMAGELENGTH, (uint32)image->GetHeight());
 556     TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
 557     TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
 558
 559     // save the image resolution if we have it
 560     int xres, yres;
 561     const wxImageResolution res = GetResolutionFromOptions(*image, &xres, &yres);
 562     uint16 tiffRes;
 563     switch ( res )
 564     {
 565         default:
 566             wxFAIL_MSG( wxT("unknown image resolution units") );
 567             // fall through
 568
 569         case wxIMAGE_RESOLUTION_NONE:
 570             tiffRes = RESUNIT_NONE;
 571             break;
 572
 573         case wxIMAGE_RESOLUTION_INCHES:
 574             tiffRes = RESUNIT_INCH;
 575             break;
 576
 577         case wxIMAGE_RESOLUTION_CM:
 578             tiffRes = RESUNIT_CENTIMETER;
 579             break;
 580     }
 581
 582     if ( tiffRes != RESUNIT_NONE )
 583     {
 584         TIFFSetField(tif, TIFFTAG_RESOLUTIONUNIT, tiffRes);
 585         TIFFSetField(tif, TIFFTAG_XRESOLUTION, (float)xres);
 586         TIFFSetField(tif, TIFFTAG_YRESOLUTION, (float)yres);
 587     }
 588
 589
 590     int spp = image->GetOptionInt(wxIMAGE_OPTION_SAMPLESPERPIXEL);
 591     if ( !spp )
 592         spp = 3;
 593
 594     int bpp = image->GetOptionInt(wxIMAGE_OPTION_BITSPERSAMPLE);
 595     if ( !bpp )
 596         bpp = 8;
 597
 598     int compression = image->GetOptionInt(wxIMAGE_OPTION_COMPRESSION);
 599     if ( !compression )
 600     {
 601         // we can't use COMPRESSION_LZW because current version of libtiff
 602         // doesn't implement it ("no longer implemented due to Unisys patent
 603         // enforcement") and other compression methods are lossy so we
 604         // shouldn't use them by default -- and the only remaining one is none
 605         compression = COMPRESSION_NONE;
 606     }
 607
 608     TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, spp);
 609     TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, bpp);
 610     TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, spp*bpp == 1 ? PHOTOMETRIC_MINISBLACK
 611                                                         : PHOTOMETRIC_RGB);
 612     TIFFSetField(tif, TIFFTAG_COMPRESSION, compression);
 613
 614     // scanlinesize if determined by spp and bpp
 615     tsize_t linebytes = (tsize_t)image->GetWidth() * spp * bpp / 8;
 616
 617     if ( (image->GetWidth() % 8 > 0) && (spp * bpp < 8) )
 618         linebytes+=1;
 619
 620     unsigned char *buf;
 621
 622     if (TIFFScanlineSize(tif) > linebytes || (spp * bpp < 24))
 623     {
 624         buf = (unsigned char *)_TIFFmalloc(TIFFScanlineSize(tif));
 625         if (!buf)
 626         {
 627             if (verbose)
 628             {
 629                 wxLogError( _("TIFF: Couldn't allocate memory.") );
 630             }
 631
 632             TIFFClose( tif );
 633
 634             return false;
 635         }
 636     }
 637     else
 638     {
 639         buf = NULL;
 640     }
 641
 642     TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP,TIFFDefaultStripSize(tif, (uint32) -1));
 643
 644     unsigned char *ptr = image->GetData();
 645     for ( int row = 0; row < image->GetHeight(); row++ )
 646     {
 647         if ( buf )
 648         {
 649             if ( spp * bpp > 1 )
 650             {
 651                 // color image
 652                 memcpy(buf, ptr, image->GetWidth());
 653             }
 654             else // black and white image
 655             {
 656                 for ( int column = 0; column < linebytes; column++ )
 657                 {
 658                     uint8 reverse = 0;
 659                     for ( int bp = 0; bp < 8; bp++ )
 660                     {
 661                         if ( ptr[column*24 + bp*3] > 127 )
 662                         {
 663                             // check only red as this is sufficient
 664                             reverse = (uint8)(reverse | 128 >> bp);
 665                         }
 666                     }
 667
 668                     buf[column] = reverse;
 669                 }
 670             }
 671         }
 672
 673         if ( TIFFWriteScanline(tif, buf ? buf : ptr, (uint32)row, 0) < 0 )
 674         {
 675             if (verbose)
 676             {
 677                 wxLogError( _("TIFF: Error writing image.") );
 678             }
 679
 680             TIFFClose( tif );
 681             if (buf)
 682                 _TIFFfree(buf);
 683
 684             return false;
 685         }
 686
 687         ptr += image->GetWidth()*3;
 688     }
 689
 690     (void) TIFFClose(tif);
 691
 692     if (buf)
 693         _TIFFfree(buf);
 694
 695     return true;
 696 }
 697
 698 bool wxTIFFHandler::DoCanRead( wxInputStream& stream )
 699 {
 700     unsigned char hdr[2];
 701
 702     if ( !stream.Read(&hdr[0], WXSIZEOF(hdr)) )     // it's ok to modify the stream position here
 703         return false;
 704
 705     return (hdr[0] == 'I' && hdr[1] == 'I') ||
 706            (hdr[0] == 'M' && hdr[1] == 'M');
 707 }
 708
 709 #endif  // wxUSE_STREAMS
 710
 711 /*static*/ wxVersionInfo wxTIFFHandler::GetLibraryVersionInfo()
 712 {
 713     int major,
 714         minor,
 715         micro;
 716
 717     const wxString ver(::TIFFGetVersion());
 718     if ( wxSscanf(ver, "LIBTIFF, Version %d.%d.%d", &major, &minor, &micro) != 3 )
 719     {
 720         wxLogDebug("Unrecognized libtiff version string \"%s\"", ver);
 721
 722         major =
 723         minor =
 724         micro = 0;
 725     }
 726
 727     wxString copyright;
 728     const wxString desc = ver.BeforeFirst('\n', &copyright);
 729     copyright.Replace("\n", "");
 730
 731     return wxVersionInfo("libtiff", major, minor, micro, desc, copyright);
 732 }
 733
 734 #endif  // wxUSE_LIBTIFF