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     image->SetOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC, photometric);
 441
 442     uint16 spp, bps, compression;
 443     /*
 444     Read some baseline TIFF tags which helps when re-saving a TIFF
 445     to be similar to the original image.
 446     */
 447     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &spp) )
 448     {
 449         image->SetOption(wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL, spp);
 450     }
 451
 452     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_BITSPERSAMPLE, &bps) )
 453     {
 454         image->SetOption(wxIMAGE_OPTION_TIFF_BITSPERSAMPLE, bps);
 455     }
 456
 457     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_COMPRESSION, &compression) )
 458     {
 459         image->SetOption(wxIMAGE_OPTION_TIFF_COMPRESSION, compression);
 460     }
 461
 462     // Set the resolution unit.
 463     wxImageResolution resUnit = wxIMAGE_RESOLUTION_NONE;
 464     uint16 tiffRes;
 465     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_RESOLUTIONUNIT, &tiffRes) )
 466     {
 467         switch (tiffRes)
 468         {
 469             default:
 470                 wxLogWarning(_("Unknown TIFF resolution unit %d ignored"),
 471                     tiffRes);
 472                 // fall through
 473
 474             case RESUNIT_NONE:
 475                 resUnit = wxIMAGE_RESOLUTION_NONE;
 476                 break;
 477
 478             case RESUNIT_INCH:
 479                 resUnit = wxIMAGE_RESOLUTION_INCHES;
 480                 break;
 481
 482             case RESUNIT_CENTIMETER:
 483                 resUnit = wxIMAGE_RESOLUTION_CM;
 484                 break;
 485         }
 486     }
 487
 488     image->SetOption(wxIMAGE_OPTION_RESOLUTIONUNIT, resUnit);
 489
 490     /*
 491     Set the image resolution if it's available. Resolution tag is not
 492     dependant on RESOLUTIONUNIT != RESUNIT_NONE (according to TIFF spec).
 493     */
 494     float resX, resY;
 495
 496     if ( TIFFGetField(tif, TIFFTAG_XRESOLUTION, &resX) )
 497     {
 498         /*
 499         Use a string value to not lose precision.
 500         rounding to int as cm and then converting to inch may
 501         result in whole integer rounding error, eg. 201 instead of 200 dpi.
 502         If an app wants an int, GetOptionInt will convert and round down.
 503         */
 504         image->SetOption(wxIMAGE_OPTION_RESOLUTIONX,
 505             wxString::FromCDouble((double) resX));
 506     }
 507
 508     if ( TIFFGetField(tif, TIFFTAG_YRESOLUTION, &resY) )
 509     {
 510         image->SetOption(wxIMAGE_OPTION_RESOLUTIONY,
 511             wxString::FromCDouble((double) resY));
 512     }
 513
 514     _TIFFfree( raster );
 515
 516     TIFFClose( tif );
 517
 518     return true;
 519 }
 520
 521 int wxTIFFHandler::DoGetImageCount( wxInputStream& stream )
 522 {
 523     TIFF *tif = TIFFwxOpen( stream, "image", "r" );
 524
 525     if (!tif)
 526         return 0;
 527
 528     int dircount = 0;  // according to the libtiff docs, dircount should be set to 1 here???
 529     do {
 530         dircount++;
 531     } while (TIFFReadDirectory(tif));
 532
 533     TIFFClose( tif );
 534
 535     // NOTE: this function modifies the current stream position but it's ok
 536     //       (see wxImageHandler::GetImageCount)
 537
 538     return dircount;
 539 }
 540
 541 bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 542 {
 543     TIFF *tif = TIFFwxOpen( stream, "image", "w" );
 544
 545     if (!tif)
 546     {
 547         if (verbose)
 548         {
 549             wxLogError( _("TIFF: Error saving image.") );
 550         }
 551
 552         return false;
 553     }
 554
 555     TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
 556     TIFFSetField(tif, TIFFTAG_IMAGEWIDTH,  (uint32)image->GetWidth());
 557     TIFFSetField(tif, TIFFTAG_IMAGELENGTH, (uint32)image->GetHeight());
 558     TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
 559     TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
 560
 561     // save the image resolution if we have it
 562     int xres, yres;
 563     const wxImageResolution res = GetResolutionFromOptions(*image, &xres, &yres);
 564     uint16 tiffRes;
 565     switch ( res )
 566     {
 567         default:
 568             wxFAIL_MSG( wxT("unknown image resolution units") );
 569             // fall through
 570
 571         case wxIMAGE_RESOLUTION_NONE:
 572             tiffRes = RESUNIT_NONE;
 573             break;
 574
 575         case wxIMAGE_RESOLUTION_INCHES:
 576             tiffRes = RESUNIT_INCH;
 577             break;
 578
 579         case wxIMAGE_RESOLUTION_CM:
 580             tiffRes = RESUNIT_CENTIMETER;
 581             break;
 582     }
 583
 584     if ( tiffRes != RESUNIT_NONE )
 585     {
 586         TIFFSetField(tif, TIFFTAG_RESOLUTIONUNIT, tiffRes);
 587         TIFFSetField(tif, TIFFTAG_XRESOLUTION, (float)xres);
 588         TIFFSetField(tif, TIFFTAG_YRESOLUTION, (float)yres);
 589     }
 590
 591
 592     int spp = image->GetOptionInt(wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL);
 593     if ( !spp )
 594         spp = 3;
 595
 596     int bps = image->GetOptionInt(wxIMAGE_OPTION_TIFF_BITSPERSAMPLE);
 597     if ( !bps )
 598     {
 599         bps = 8;
 600     }
 601     else if (bps == 1)
 602     {
 603         // One bit per sample combined with 3 samples per pixel is
 604         // not allowed and crashes libtiff.
 605         spp = 1;
 606     }
 607
 608     int photometric = PHOTOMETRIC_RGB;
 609
 610     if ( image->HasOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC) )
 611     {
 612         photometric = image->GetOptionInt(wxIMAGE_OPTION_TIFF_PHOTOMETRIC);
 613         if (photometric == PHOTOMETRIC_MINISWHITE
 614             || photometric == PHOTOMETRIC_MINISBLACK)
 615         {
 616             // either b/w or greyscale
 617             spp = 1;
 618         }
 619     }
 620     else if (spp == 1)
 621     {
 622         photometric = PHOTOMETRIC_MINISWHITE;
 623     }
 624
 625     const bool isColouredImage = (spp > 1)
 626         && (photometric != PHOTOMETRIC_MINISWHITE)
 627         && (photometric != PHOTOMETRIC_MINISBLACK);
 628
 629     int compression = image->GetOptionInt(wxIMAGE_OPTION_TIFF_COMPRESSION);
 630     if ( !compression )
 631     {
 632         // we can't use COMPRESSION_LZW because current version of libtiff
 633         // doesn't implement it ("no longer implemented due to Unisys patent
 634         // enforcement") and other compression methods are lossy so we
 635         // shouldn't use them by default -- and the only remaining one is none
 636         compression = COMPRESSION_NONE;
 637     }
 638
 639     TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, spp);
 640     TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, bps);
 641     TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, photometric);
 642     TIFFSetField(tif, TIFFTAG_COMPRESSION, compression);
 643
 644     // scanlinesize if determined by spp and bps
 645     tsize_t linebytes = (tsize_t)image->GetWidth() * spp * bps / 8;
 646
 647     if ( (image->GetWidth() % 8 > 0) && (spp * bps < 8) )
 648         linebytes+=1;
 649
 650     unsigned char *buf;
 651
 652     if (TIFFScanlineSize(tif) > linebytes || !isColouredImage)
 653     {
 654         buf = (unsigned char *)_TIFFmalloc(TIFFScanlineSize(tif));
 655         if (!buf)
 656         {
 657             if (verbose)
 658             {
 659                 wxLogError( _("TIFF: Couldn't allocate memory.") );
 660             }
 661
 662             TIFFClose( tif );
 663
 664             return false;
 665         }
 666     }
 667     else
 668     {
 669         buf = NULL;
 670     }
 671
 672     TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP,TIFFDefaultStripSize(tif, (uint32) -1));
 673
 674     const bool minIsWhite = (photometric == PHOTOMETRIC_MINISWHITE);
 675     unsigned char *ptr = image->GetData();
 676     for ( int row = 0; row < image->GetHeight(); row++ )
 677     {
 678         if ( buf )
 679         {
 680             if (isColouredImage)
 681             {
 682                 // color image
 683                 memcpy(buf, ptr, image->GetWidth());
 684             }
 685             else if (spp * bps == 8) // greyscale image
 686             {
 687                 for ( int column = 0; column < linebytes; column++ )
 688                 {
 689                     uint8 value = ptr[column*3 + 1];
 690                     if (minIsWhite)
 691                     {
 692                         value = 255 - value;
 693                     }
 694
 695                     buf[column] = value;
 696                 }
 697             }
 698             else // black and white image
 699             {
 700                 for ( int column = 0; column < linebytes; column++ )
 701                 {
 702                     uint8 reverse = 0;
 703                     for ( int bp = 0; bp < 8; bp++ )
 704                     {
 705                         if ( (ptr[column*24 + bp*3 + 1] <=127) == minIsWhite )
 706                         {
 707                             // check only green as this is sufficient
 708                             reverse = (uint8)(reverse | 128 >> bp);
 709                         }
 710                     }
 711
 712                     buf[column] = reverse;
 713                 }
 714             }
 715         }
 716
 717         if ( TIFFWriteScanline(tif, buf ? buf : ptr, (uint32)row, 0) < 0 )
 718         {
 719             if (verbose)
 720             {
 721                 wxLogError( _("TIFF: Error writing image.") );
 722             }
 723
 724             TIFFClose( tif );
 725             if (buf)
 726                 _TIFFfree(buf);
 727
 728             return false;
 729         }
 730
 731         ptr += image->GetWidth()*3;
 732     }
 733
 734     (void) TIFFClose(tif);
 735
 736     if (buf)
 737         _TIFFfree(buf);
 738
 739     return true;
 740 }
 741
 742 bool wxTIFFHandler::DoCanRead( wxInputStream& stream )
 743 {
 744     unsigned char hdr[2];
 745
 746     if ( !stream.Read(&hdr[0], WXSIZEOF(hdr)) )     // it's ok to modify the stream position here
 747         return false;
 748
 749     return (hdr[0] == 'I' && hdr[1] == 'I') ||
 750            (hdr[0] == 'M' && hdr[1] == 'M');
 751 }
 752
 753 #endif  // wxUSE_STREAMS
 754
 755 /*static*/ wxVersionInfo wxTIFFHandler::GetLibraryVersionInfo()
 756 {
 757     int major,
 758         minor,
 759         micro;
 760
 761     const wxString ver(::TIFFGetVersion());
 762     if ( wxSscanf(ver, "LIBTIFF, Version %d.%d.%d", &major, &minor, &micro) != 3 )
 763     {
 764         wxLogDebug("Unrecognized libtiff version string \"%s\"", ver);
 765
 766         major =
 767         minor =
 768         micro = 0;
 769     }
 770
 771     wxString copyright;
 772     const wxString desc = ver.BeforeFirst('\n', &copyright);
 773     copyright.Replace("\n", "");
 774
 775     return wxVersionInfo("libtiff", major, minor, micro, desc, copyright);
 776 }
 777
 778 #endif  // wxUSE_LIBTIFF