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_TIFF;
 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 (!TIFFReadRGBAImageOriented( tif, w, h, raster, ORIENTATION_TOPLEFT, 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
 413     unsigned char *alpha = image->GetAlpha();
 414
 415     uint32 pos = 0;
 416
 417     for (uint32 i = 0; i < h; i++)
 418     {
 419         for (uint32 j = 0; j < w; j++)
 420         {
 421             *(ptr++) = (unsigned char)TIFFGetR(raster[pos]);
 422             *(ptr++) = (unsigned char)TIFFGetG(raster[pos]);
 423             *(ptr++) = (unsigned char)TIFFGetB(raster[pos]);
 424             if ( hasAlpha )
 425                 *(alpha++) = (unsigned char)TIFFGetA(raster[pos]);
 426
 427             pos++;
 428         }
 429     }
 430
 431
 432     image->SetOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC, photometric);
 433
 434     uint16 spp, bps, compression;
 435     /*
 436     Read some baseline TIFF tags which helps when re-saving a TIFF
 437     to be similar to the original image.
 438     */
 439     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_SAMPLESPERPIXEL, &spp) )
 440     {
 441         image->SetOption(wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL, spp);
 442     }
 443
 444     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_BITSPERSAMPLE, &bps) )
 445     {
 446         image->SetOption(wxIMAGE_OPTION_TIFF_BITSPERSAMPLE, bps);
 447     }
 448
 449     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_COMPRESSION, &compression) )
 450     {
 451         image->SetOption(wxIMAGE_OPTION_TIFF_COMPRESSION, compression);
 452     }
 453
 454     // Set the resolution unit.
 455     wxImageResolution resUnit = wxIMAGE_RESOLUTION_NONE;
 456     uint16 tiffRes;
 457     if ( TIFFGetFieldDefaulted(tif, TIFFTAG_RESOLUTIONUNIT, &tiffRes) )
 458     {
 459         switch (tiffRes)
 460         {
 461             default:
 462                 wxLogWarning(_("Unknown TIFF resolution unit %d ignored"),
 463                     tiffRes);
 464                 // fall through
 465
 466             case RESUNIT_NONE:
 467                 resUnit = wxIMAGE_RESOLUTION_NONE;
 468                 break;
 469
 470             case RESUNIT_INCH:
 471                 resUnit = wxIMAGE_RESOLUTION_INCHES;
 472                 break;
 473
 474             case RESUNIT_CENTIMETER:
 475                 resUnit = wxIMAGE_RESOLUTION_CM;
 476                 break;
 477         }
 478     }
 479
 480     image->SetOption(wxIMAGE_OPTION_RESOLUTIONUNIT, resUnit);
 481
 482     /*
 483     Set the image resolution if it's available. Resolution tag is not
 484     dependant on RESOLUTIONUNIT != RESUNIT_NONE (according to TIFF spec).
 485     */
 486     float resX, resY;
 487
 488     if ( TIFFGetField(tif, TIFFTAG_XRESOLUTION, &resX) )
 489     {
 490         /*
 491         Use a string value to not lose precision.
 492         rounding to int as cm and then converting to inch may
 493         result in whole integer rounding error, eg. 201 instead of 200 dpi.
 494         If an app wants an int, GetOptionInt will convert and round down.
 495         */
 496         image->SetOption(wxIMAGE_OPTION_RESOLUTIONX,
 497             wxString::FromCDouble((double) resX));
 498     }
 499
 500     if ( TIFFGetField(tif, TIFFTAG_YRESOLUTION, &resY) )
 501     {
 502         image->SetOption(wxIMAGE_OPTION_RESOLUTIONY,
 503             wxString::FromCDouble((double) resY));
 504     }
 505
 506     _TIFFfree( raster );
 507
 508     TIFFClose( tif );
 509
 510     return true;
 511 }
 512
 513 int wxTIFFHandler::DoGetImageCount( wxInputStream& stream )
 514 {
 515     TIFF *tif = TIFFwxOpen( stream, "image", "r" );
 516
 517     if (!tif)
 518         return 0;
 519
 520     int dircount = 0;  // according to the libtiff docs, dircount should be set to 1 here???
 521     do {
 522         dircount++;
 523     } while (TIFFReadDirectory(tif));
 524
 525     TIFFClose( tif );
 526
 527     // NOTE: this function modifies the current stream position but it's ok
 528     //       (see wxImageHandler::GetImageCount)
 529
 530     return dircount;
 531 }
 532
 533 bool wxTIFFHandler::SaveFile( wxImage *image, wxOutputStream& stream, bool verbose )
 534 {
 535     TIFF *tif = TIFFwxOpen( stream, "image", "w" );
 536
 537     if (!tif)
 538     {
 539         if (verbose)
 540         {
 541             wxLogError( _("TIFF: Error saving image.") );
 542         }
 543
 544         return false;
 545     }
 546
 547     TIFFSetField(tif, TIFFTAG_IMAGEWIDTH,  (uint32)image->GetWidth());
 548     TIFFSetField(tif, TIFFTAG_IMAGELENGTH, (uint32)image->GetHeight());
 549     TIFFSetField(tif, TIFFTAG_ORIENTATION, ORIENTATION_TOPLEFT);
 550     TIFFSetField(tif, TIFFTAG_PLANARCONFIG, PLANARCONFIG_CONTIG);
 551
 552     // save the image resolution if we have it
 553     int xres, yres;
 554     const wxImageResolution res = GetResolutionFromOptions(*image, &xres, &yres);
 555     uint16 tiffRes;
 556     switch ( res )
 557     {
 558         default:
 559             wxFAIL_MSG( wxT("unknown image resolution units") );
 560             // fall through
 561
 562         case wxIMAGE_RESOLUTION_NONE:
 563             tiffRes = RESUNIT_NONE;
 564             break;
 565
 566         case wxIMAGE_RESOLUTION_INCHES:
 567             tiffRes = RESUNIT_INCH;
 568             break;
 569
 570         case wxIMAGE_RESOLUTION_CM:
 571             tiffRes = RESUNIT_CENTIMETER;
 572             break;
 573     }
 574
 575     if ( tiffRes != RESUNIT_NONE )
 576     {
 577         TIFFSetField(tif, TIFFTAG_RESOLUTIONUNIT, tiffRes);
 578         TIFFSetField(tif, TIFFTAG_XRESOLUTION, (float)xres);
 579         TIFFSetField(tif, TIFFTAG_YRESOLUTION, (float)yres);
 580     }
 581
 582
 583     int spp = image->GetOptionInt(wxIMAGE_OPTION_TIFF_SAMPLESPERPIXEL);
 584     if ( !spp )
 585         spp = 3;
 586
 587     int bps = image->GetOptionInt(wxIMAGE_OPTION_TIFF_BITSPERSAMPLE);
 588     if ( !bps )
 589     {
 590         bps = 8;
 591     }
 592     else if (bps == 1)
 593     {
 594         // One bit per sample combined with 3 samples per pixel is
 595         // not allowed and crashes libtiff.
 596         spp = 1;
 597     }
 598
 599     int photometric = PHOTOMETRIC_RGB;
 600
 601     if ( image->HasOption(wxIMAGE_OPTION_TIFF_PHOTOMETRIC) )
 602     {
 603         photometric = image->GetOptionInt(wxIMAGE_OPTION_TIFF_PHOTOMETRIC);
 604         if (photometric == PHOTOMETRIC_MINISWHITE
 605             || photometric == PHOTOMETRIC_MINISBLACK)
 606         {
 607             // either b/w or greyscale
 608             spp = 1;
 609         }
 610     }
 611     else if (spp == 1)
 612     {
 613         photometric = PHOTOMETRIC_MINISWHITE;
 614     }
 615
 616     const bool isColouredImage = (spp > 1)
 617         && (photometric != PHOTOMETRIC_MINISWHITE)
 618         && (photometric != PHOTOMETRIC_MINISBLACK);
 619
 620     int compression = image->GetOptionInt(wxIMAGE_OPTION_TIFF_COMPRESSION);
 621     if ( !compression )
 622     {
 623         // we can't use COMPRESSION_LZW because current version of libtiff
 624         // doesn't implement it ("no longer implemented due to Unisys patent
 625         // enforcement") and other compression methods are lossy so we
 626         // shouldn't use them by default -- and the only remaining one is none
 627         compression = COMPRESSION_NONE;
 628     }
 629
 630     TIFFSetField(tif, TIFFTAG_SAMPLESPERPIXEL, spp);
 631     TIFFSetField(tif, TIFFTAG_BITSPERSAMPLE, bps);
 632     TIFFSetField(tif, TIFFTAG_PHOTOMETRIC, photometric);
 633     TIFFSetField(tif, TIFFTAG_COMPRESSION, compression);
 634
 635     // scanlinesize is determined by spp and bps
 636     const tsize_t linebytes =
 637         (tsize_t)((image->GetWidth() * spp * bps + 7) / 8);
 638
 639     unsigned char *buf;
 640
 641     if (TIFFScanlineSize(tif) > linebytes || !isColouredImage)
 642     {
 643         buf = (unsigned char *)_TIFFmalloc(TIFFScanlineSize(tif));
 644         if (!buf)
 645         {
 646             if (verbose)
 647             {
 648                 wxLogError( _("TIFF: Couldn't allocate memory.") );
 649             }
 650
 651             TIFFClose( tif );
 652
 653             return false;
 654         }
 655     }
 656     else
 657     {
 658         buf = NULL;
 659     }
 660
 661     TIFFSetField(tif, TIFFTAG_ROWSPERSTRIP,TIFFDefaultStripSize(tif, (uint32) -1));
 662
 663     const int bitsPerPixel = spp * bps;
 664     const int pixelsPerByte = 8 / bitsPerPixel;
 665     int remainingPixelCount = 0;
 666
 667     if (pixelsPerByte)
 668     {
 669         // How many pixels to write in the last byte column?
 670         remainingPixelCount = image->GetWidth() % pixelsPerByte;
 671         if (!remainingPixelCount) remainingPixelCount = 8;
 672     }
 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                     int pixelsPerByteCount = (column + 1 != linebytes)
 704                         ? pixelsPerByte
 705                         : remainingPixelCount;
 706                     for ( int bp = 0; bp < pixelsPerByteCount; bp++ )
 707                     {
 708                         if ( (ptr[column*24 + bp*3 + 1] <=127) == minIsWhite )
 709                         {
 710                             // check only green as this is sufficient
 711                             reverse = (uint8)(reverse | 128 >> bp);
 712                         }
 713                     }
 714
 715                     buf[column] = reverse;
 716                 }
 717             }
 718         }
 719
 720         if ( TIFFWriteScanline(tif, buf ? buf : ptr, (uint32)row, 0) < 0 )
 721         {
 722             if (verbose)
 723             {
 724                 wxLogError( _("TIFF: Error writing image.") );
 725             }
 726
 727             TIFFClose( tif );
 728             if (buf)
 729                 _TIFFfree(buf);
 730
 731             return false;
 732         }
 733
 734         ptr += image->GetWidth()*3;
 735     }
 736
 737     (void) TIFFClose(tif);
 738
 739     if (buf)
 740         _TIFFfree(buf);
 741
 742     return true;
 743 }
 744
 745 bool wxTIFFHandler::DoCanRead( wxInputStream& stream )
 746 {
 747     unsigned char hdr[2];
 748
 749     if ( !stream.Read(&hdr[0], WXSIZEOF(hdr)) )     // it's ok to modify the stream position here
 750         return false;
 751
 752     return (hdr[0] == 'I' && hdr[1] == 'I') ||
 753            (hdr[0] == 'M' && hdr[1] == 'M');
 754 }
 755
 756 #endif  // wxUSE_STREAMS
 757
 758 /*static*/ wxVersionInfo wxTIFFHandler::GetLibraryVersionInfo()
 759 {
 760     int major,
 761         minor,
 762         micro;
 763
 764     const wxString ver(::TIFFGetVersion());
 765     if ( wxSscanf(ver, "LIBTIFF, Version %d.%d.%d", &major, &minor, &micro) != 3 )
 766     {
 767         wxLogDebug("Unrecognized libtiff version string \"%s\"", ver);
 768
 769         major =
 770         minor =
 771         micro = 0;
 772     }
 773
 774     wxString copyright;
 775     const wxString desc = ver.BeforeFirst('\n', &copyright);
 776     copyright.Replace("\n", "");
 777
 778     return wxVersionInfo("libtiff", major, minor, micro, desc, copyright);
 779 }
 780
 781 #endif  // wxUSE_LIBTIFF