src/common/imagtga.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        src/common/imagtga.cpp
   3 // Purpose:     wxImage TGA handler
   4 // Author:      Seth Jackson
   5 // CVS-ID:      $Id$
   6 // Copyright:   (c) 2005 Seth Jackson
   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_TGA
  26
  27 #ifndef WX_PRECOMP
  28     #include "wx/palette.h"
  29 #endif
  30
  31 #include "wx/imagtga.h"
  32 #include "wx/log.h"
  33 #include "wx/scopeguard.h"
  34
  35 // ----------------------------------------------------------------------------
  36 // constants
  37 // ----------------------------------------------------------------------------
  38
  39 // TGA error codes.
  40 enum
  41 {
  42     wxTGA_OK,
  43     wxTGA_INVFORMAT,
  44     wxTGA_MEMERR,
  45     wxTGA_IOERR
  46 };
  47
  48 // TGA header bytes.
  49 enum
  50 {
  51     HDR_OFFSET = 0,
  52     HDR_COLORTYPE  = 1,
  53     HDR_IMAGETYPE = 2,
  54     HDR_PALETTESTART = 3,
  55     HDR_PALETTELENGTH = 5,
  56     HDR_PALETTEBITS = 7,
  57     HDR_XORIGIN = 8,
  58     HDR_YORIGIN = 10,
  59     HDR_WIDTH = 12,
  60     HDR_HEIGHT = 14,
  61     HDR_BPP = 16,
  62     HDR_ORIENTATION = 17,
  63     HDR_SIZE
  64 };
  65
  66 // TGA color types.
  67 enum
  68 {
  69     wxTGA_UNMAPPED = 0,
  70     wxTGA_MAPPED = 1
  71 };
  72
  73 // ============================================================================
  74 // implementation
  75 // ============================================================================
  76
  77 IMPLEMENT_DYNAMIC_CLASS(wxTGAHandler, wxImageHandler)
  78
  79 #if wxUSE_STREAMS
  80
  81 // ----------------------------------------------------------------------------
  82 // worker functions
  83 // ----------------------------------------------------------------------------
  84
  85 static
  86 void FlipTGA(unsigned char* imageData, int width, int height, short pixelSize)
  87 {
  88     int lineLength = width * pixelSize;
  89     unsigned char *line1 = imageData;
  90     unsigned char *line2 = &imageData[lineLength * (height - 1)];
  91
  92     unsigned char temp;
  93     for ( ; line1 < line2; line2 -= (lineLength * 2))
  94     {
  95         for (int index = 0; index < lineLength; line1++, line2++, index++)
  96         {
  97             temp = *line1;
  98             *line1 = *line2;
  99             *line2 = temp;
 100         }
 101     }
 102 }
 103
 104 // return wxTGA_OK or wxTGA_IOERR
 105 static
 106 int DecodeRLE(unsigned char* imageData, unsigned long imageSize,
 107                short pixelSize, wxInputStream& stream)
 108 {
 109     unsigned long index = 0;
 110     unsigned char current;
 111     unsigned int length;
 112     unsigned char buf[4];
 113
 114     while (index < imageSize)
 115     {
 116         int ch = stream.GetC();
 117         if ( ch == wxEOF )
 118             return wxTGA_IOERR;
 119
 120         current = ch;
 121
 122         // RLE packet.
 123         if ( current & 0x80 )
 124         {
 125             // Get the run length of the packet.
 126             current &= 0x7f;
 127
 128             current++;
 129
 130             length = current;
 131
 132             index += current * pixelSize;
 133
 134             if (index >= imageSize)
 135             {
 136                 return wxTGA_IOERR;
 137             }
 138
 139             // Repeat the pixel length times.
 140             if ( !stream.Read(buf, pixelSize) )
 141                 return wxTGA_IOERR;
 142
 143             for (unsigned int i = 0; i < length; i++)
 144             {
 145                 memcpy(imageData, buf, pixelSize);
 146
 147                 imageData += pixelSize;
 148             }
 149         }
 150         else // Raw packet.
 151         {
 152             // Get the run length of the packet.
 153             current++;
 154
 155             length = current * pixelSize;
 156
 157             index += length;
 158
 159             if (index >= imageSize)
 160             {
 161                 return wxTGA_IOERR;
 162             }
 163
 164             // Write the next length pixels directly to the image data.
 165             if ( !stream.Read(imageData, length) )
 166                 return wxTGA_IOERR;
 167
 168             imageData += length;
 169         }
 170     }
 171
 172     return wxTGA_OK;
 173 }
 174
 175 /*
 176 Mimic the behaviour of wxPalette.GetRGB and the way the TGA image handler
 177 used it. That is: don't check the return value of GetRGB and continue decoding
 178 using previous RGB values.
 179
 180 It might be better to check for palette index bounds and stop decoding if
 181 it's out of range (and add something like wxTGA_DATAERR to indicate unexpected
 182 pixel data).
 183 */
 184 static
 185 void Palette_GetRGB(const unsigned char *palette, unsigned int paletteCount,
 186     unsigned int index,
 187     unsigned char *red, unsigned char *green, unsigned char *blue)
 188 {
 189     if (index >= paletteCount)
 190     {
 191         return;
 192     }
 193
 194     *red   = palette[index];
 195     *green = palette[(paletteCount * 1) + index];
 196     *blue  = palette[(paletteCount * 2) + index];
 197 }
 198
 199 static
 200 void Palette_SetRGB(unsigned char *palette, unsigned int paletteCount,
 201     unsigned int index,
 202     unsigned char red, unsigned char green, unsigned char blue)
 203 {
 204     palette[index] = red;
 205     palette[(paletteCount * 1) + index] = green;
 206     palette[(paletteCount * 2) + index] = blue;
 207 }
 208
 209 static
 210 int ReadTGA(wxImage* image, wxInputStream& stream)
 211 {
 212     // Read in the TGA header
 213     unsigned char hdr[HDR_SIZE];
 214     stream.Read(hdr, HDR_SIZE);
 215
 216     short offset = hdr[HDR_OFFSET] + HDR_SIZE;
 217     short colorType = hdr[HDR_COLORTYPE];
 218     short imageType = hdr[HDR_IMAGETYPE];
 219     unsigned int paletteLength = hdr[HDR_PALETTELENGTH]
 220         + 256 * hdr[HDR_PALETTELENGTH + 1];
 221     int width = (hdr[HDR_WIDTH] + 256 * hdr[HDR_WIDTH + 1]) -
 222                 (hdr[HDR_XORIGIN] + 256 * hdr[HDR_XORIGIN + 1]);
 223     int height = (hdr[HDR_HEIGHT] + 256 * hdr[HDR_HEIGHT + 1]) -
 224                  (hdr[HDR_YORIGIN] + 256 * hdr[HDR_YORIGIN + 1]);
 225     short bpp = hdr[HDR_BPP];
 226     short orientation = hdr[HDR_ORIENTATION] & 0x20;
 227
 228     image->Create(width, height);
 229
 230     if (!image->IsOk())
 231     {
 232         return wxTGA_MEMERR;
 233     }
 234
 235     const short pixelSize = bpp / 8;
 236
 237     const unsigned long imageSize = width * height * pixelSize;
 238
 239     unsigned char *imageData = (unsigned char* )malloc(imageSize);
 240
 241     if (!imageData)
 242     {
 243         return wxTGA_MEMERR;
 244     }
 245
 246     wxON_BLOCK_EXIT1(free, imageData);
 247
 248     unsigned char *dst = image->GetData();
 249
 250     unsigned char* alpha = NULL;
 251     if (bpp == 16 || bpp == 32)
 252     {
 253         image->SetAlpha();
 254
 255         alpha = image->GetAlpha();
 256     }
 257
 258     // Seek from the offset we got from the TGA header.
 259     if (stream.SeekI(offset, wxFromStart) == wxInvalidOffset)
 260         return wxTGA_INVFORMAT;
 261
 262     unsigned char *palette = NULL;
 263     // Load a palette if we have one.
 264     if (colorType == wxTGA_MAPPED)
 265     {
 266         unsigned char buf[3];
 267
 268         palette = (unsigned char *) malloc(paletteLength * 3);
 269
 270         for (unsigned int i = 0; i < paletteLength; i++)
 271         {
 272             stream.Read(buf, 3);
 273
 274             Palette_SetRGB(palette, paletteLength, i, buf[2], buf[1], buf[0]);
 275         }
 276
 277 #if wxUSE_PALETTE
 278         // Set the palette of the image.
 279         image->SetPalette(wxPalette((int) paletteLength, &palette[0],
 280             &palette[paletteLength * 1], &palette[paletteLength * 2]));
 281 #endif // wxUSE_PALETTE
 282
 283     }
 284
 285     wxON_BLOCK_EXIT1(free, palette);
 286
 287     // Handle the various TGA formats we support.
 288
 289     switch (imageType)
 290     {
 291         // Raw indexed.
 292
 293         case 1:
 294         {
 295             unsigned char r = 0;
 296             unsigned char g = 0;
 297             unsigned char b = 0;
 298
 299             // No compression read the data directly to imageData.
 300
 301             stream.Read(imageData, imageSize);
 302
 303             // If orientation == 0, then the image is stored upside down.
 304             // We need to store it right side up.
 305
 306             if (orientation == 0)
 307             {
 308                 FlipTGA(imageData, width, height, pixelSize);
 309             }
 310
 311             // Handle the different pixel depths.
 312
 313             switch (bpp)
 314             {
 315                 // 8 bpp.
 316
 317                 case 8:
 318                 {
 319                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 320                     {
 321                         Palette_GetRGB(palette, paletteLength,
 322                             imageData[index], &r, &g, &b);
 323
 324                         *(dst++) = r;
 325                         *(dst++) = g;
 326                         *(dst++) = b;
 327                     }
 328                 }
 329                 break;
 330
 331                 // 16 bpp.
 332
 333                 case 16:
 334                 {
 335                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 336                     {
 337                         Palette_GetRGB(palette, paletteLength,
 338                             imageData[index], &r, &g, &b);
 339
 340                         *(dst++) = r;
 341                         *(dst++) = g;
 342                         *(dst++) = b;
 343                         *(alpha++) = (imageData[index + 1] & 0x80) ? 0 : 255;
 344                     }
 345                 }
 346                 break;
 347
 348                 default:
 349                     return wxTGA_INVFORMAT;
 350             }
 351         }
 352         break;
 353
 354         // Raw RGB.
 355
 356         case 2:
 357         {
 358             // No compression read the data directly to imageData.
 359
 360             stream.Read(imageData, imageSize);
 361
 362             // If orientation == 0, then the image is stored upside down.
 363             // We need to store it right side up.
 364
 365             if (orientation == 0)
 366             {
 367                 FlipTGA(imageData, width, height, pixelSize);
 368             }
 369
 370             // Handle the different pixel depths.
 371
 372             switch (bpp)
 373             {
 374                 //16 bpp.
 375
 376                 case 16:
 377                 {
 378                     unsigned char temp;
 379
 380                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 381                     {
 382                         temp = (imageData[index + 1] & 0x7c) << 1;
 383                         temp |= temp >> 5;
 384                         *(dst++) = temp;
 385
 386                         temp = ((imageData[index + 1] & 0x03) << 6) | ((imageData[index] & 0xe0) >> 2);
 387                         temp |= temp >> 5;
 388                         *(dst++) = temp;
 389
 390                         temp = (imageData[index] & 0x1f) << 3;
 391                         temp |= temp >> 5;
 392                         *(dst++) = temp;
 393
 394                         *(alpha++) = (imageData[index + 1] & 0x80) ? 0 : 255;
 395                     }
 396                 }
 397                 break;
 398
 399                 // 24 bpp.
 400
 401                 case 24:
 402                 {
 403                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 404                     {
 405                         *(dst++) = imageData[index + 2];
 406                         *(dst++) = imageData[index + 1];
 407                         *(dst++) = imageData[index];
 408                     }
 409                 }
 410                 break;
 411
 412                 // 32 bpp.
 413
 414                 case 32:
 415                 {
 416                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 417                     {
 418                         *(dst++) = imageData[index + 2];
 419                         *(dst++) = imageData[index + 1];
 420                         *(dst++) = imageData[index];
 421                         *(alpha++) = imageData[index + 3];
 422                     }
 423                 }
 424                 break;
 425
 426                 default:
 427                     return wxTGA_INVFORMAT;
 428             }
 429         }
 430         break;
 431
 432         // Raw grayscale.
 433
 434         case 3:
 435         {
 436             // No compression read the data directly to imageData.
 437
 438             stream.Read(imageData, imageSize);
 439
 440             // If orientation == 0, then the image is stored upside down.
 441             // We need to store it right side up.
 442
 443             if (orientation == 0)
 444             {
 445                 FlipTGA(imageData, width, height, pixelSize);
 446             }
 447
 448             // Handle the different pixel depths.
 449
 450             switch (bpp)
 451             {
 452                 // 8 bpp.
 453
 454                 case 8:
 455                 {
 456                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 457                     {
 458                         *(dst++) = imageData[index];
 459                         *(dst++) = imageData[index];
 460                         *(dst++) = imageData[index];
 461                     }
 462                 }
 463                 break;
 464
 465                 // 16 bpp.
 466
 467                 case 16:
 468                 {
 469                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 470                     {
 471                         *(dst++) = imageData[index];
 472                         *(dst++) = imageData[index];
 473                         *(dst++) = imageData[index];
 474                         *(alpha++) = imageData[index + 1];
 475                     }
 476                 }
 477                 break;
 478
 479                 default:
 480                     return wxTGA_INVFORMAT;
 481             }
 482         }
 483         break;
 484
 485         // RLE indexed.
 486
 487         case 9:
 488         {
 489             unsigned char r = 0;
 490             unsigned char g = 0;
 491             unsigned char b = 0;
 492
 493             // Decode the RLE data.
 494
 495             int rc =  DecodeRLE(imageData, imageSize, pixelSize, stream);
 496             if ( rc != wxTGA_OK )
 497                 return rc;
 498
 499             // If orientation == 0, then the image is stored upside down.
 500             // We need to store it right side up.
 501
 502             if (orientation == 0)
 503             {
 504                 FlipTGA(imageData, width, height, pixelSize);
 505             }
 506
 507             // Handle the different pixel depths.
 508
 509             switch (bpp)
 510             {
 511                 // 8 bpp.
 512
 513                 case 8:
 514                 {
 515                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 516                     {
 517                         Palette_GetRGB(palette, paletteLength,
 518                             imageData[index], &r, &g, &b);
 519
 520                         *(dst++) = r;
 521                         *(dst++) = g;
 522                         *(dst++) = b;
 523                     }
 524                 }
 525                 break;
 526
 527                 // 16 bpp.
 528
 529                 case 16:
 530                 {
 531                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 532                     {
 533                         Palette_GetRGB(palette, paletteLength,
 534                             imageData[index], &r, &g, &b);
 535
 536                         *(dst++) = r;
 537                         *(dst++) = g;
 538                         *(dst++) = b;
 539                         *(alpha++) = (imageData[index + 1] & 0x80) ? 0 : 255;
 540                     }
 541                 }
 542                 break;
 543
 544                 default:
 545                     return wxTGA_INVFORMAT;
 546             }
 547         }
 548         break;
 549
 550         // RLE RGB.
 551
 552         case 10:
 553         {
 554             // Decode the RLE data.
 555
 556             int rc = DecodeRLE(imageData, imageSize, pixelSize, stream);
 557             if ( rc != wxTGA_OK )
 558                 return rc;
 559
 560             // If orientation == 0, then the image is stored upside down.
 561             // We need to store it right side up.
 562
 563             if (orientation == 0)
 564             {
 565                 FlipTGA(imageData, width, height, pixelSize);
 566             }
 567
 568             // Handle the different pixel depths.
 569
 570             switch (bpp)
 571             {
 572                 //16 bpp.
 573
 574                 case 16:
 575                 {
 576                     unsigned char temp;
 577
 578                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 579                     {
 580                         temp = (imageData[index + 1] & 0x7c) << 1;
 581                         temp |= temp >> 5;
 582                         *(dst++) = temp;
 583
 584                         temp = ((imageData[index + 1] & 0x03) << 6) | ((imageData[index] & 0xe0) >> 2);
 585                         temp |= temp >> 5;
 586                         *(dst++) = temp;
 587
 588                         temp = (imageData[index] & 0x1f) << 3;
 589                         temp |= temp >> 5;
 590                         *(dst++) = temp;
 591
 592                         *(alpha++) = (imageData[index + 1] & 0x80) ? 0 : 255;
 593                     }
 594                 }
 595                 break;
 596
 597                 // 24 bpp.
 598
 599                 case 24:
 600                 {
 601                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 602                     {
 603                         *(dst++) = imageData[index + 2];
 604                         *(dst++) = imageData[index + 1];
 605                         *(dst++) = imageData[index];
 606                     }
 607                 }
 608                 break;
 609
 610                 // 32 bpp.
 611
 612                 case 32:
 613                 {
 614                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 615                     {
 616                         *(dst++) = imageData[index + 2];
 617                         *(dst++) = imageData[index + 1];
 618                         *(dst++) = imageData[index];
 619                         *(alpha++) = imageData[index + 3];
 620                     }
 621                 }
 622                 break;
 623
 624                 default:
 625                     return wxTGA_INVFORMAT;
 626             }
 627         }
 628         break;
 629
 630         // RLE grayscale.
 631
 632         case 11:
 633         {
 634             // Decode the RLE data.
 635
 636             int rc = DecodeRLE(imageData, imageSize, pixelSize, stream);
 637             if ( rc != wxTGA_OK )
 638                 return rc;
 639
 640             // If orientation == 0, then the image is stored upside down.
 641             // We need to store it right side up.
 642
 643             if (orientation == 0)
 644             {
 645                 FlipTGA(imageData, width, height, pixelSize);
 646             }
 647
 648             // Handle the different pixel depths.
 649
 650             switch (bpp)
 651             {
 652                 // 8 bpp.
 653
 654                 case 8:
 655                 {
 656                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 657                     {
 658                         *(dst++) = imageData[index];
 659                         *(dst++) = imageData[index];
 660                         *(dst++) = imageData[index];
 661                     }
 662                 }
 663                 break;
 664
 665                 // 16 bpp.
 666
 667                 case 16:
 668                 {
 669                     for (unsigned long index = 0; index < imageSize; index += pixelSize)
 670                     {
 671                         *(dst++) = imageData[index];
 672                         *(dst++) = imageData[index];
 673                         *(dst++) = imageData[index];
 674                         *(alpha++) = imageData[index + 1];
 675                     }
 676                 }
 677                 break;
 678
 679                 default:
 680                     return wxTGA_INVFORMAT;
 681             }
 682         }
 683         break;
 684
 685         default:
 686             return wxTGA_INVFORMAT;
 687     }
 688
 689     return wxTGA_OK;
 690 }
 691
 692 static
 693 int SaveTGA(const wxImage& image, wxOutputStream *stream)
 694 {
 695     bool hasAlpha = image.HasAlpha();
 696     unsigned bytesPerPixel = 3 + (hasAlpha ? 1 : 0);
 697     wxSize size = image.GetSize();
 698     size_t scanlineSize = size.x * bytesPerPixel;
 699     unsigned char *scanlineData = (unsigned char *) malloc(scanlineSize);
 700     if (!scanlineData)
 701     {
 702         return wxTGA_MEMERR;
 703     }
 704
 705     wxON_BLOCK_EXIT1(free, scanlineData);
 706
 707     // Compose and write the TGA header
 708     unsigned char hdr[HDR_SIZE];
 709     (void) memset(&hdr, 0, HDR_SIZE);
 710
 711     hdr[HDR_COLORTYPE] = wxTGA_UNMAPPED;
 712     hdr[HDR_IMAGETYPE] = 2 /* Uncompressed truecolour */;
 713
 714     hdr[HDR_WIDTH] =  size.x & 0xFF;
 715     hdr[HDR_WIDTH + 1] =  (size.x >> 8) & 0xFF;
 716
 717     hdr[HDR_HEIGHT] =  size.y & 0xFF;
 718     hdr[HDR_HEIGHT + 1] =  (size.y >> 8) & 0xFF;
 719
 720     hdr[HDR_BPP] = hasAlpha ? 32 : 24;
 721     hdr[HDR_ORIENTATION] = 1 << 5; // set bit to indicate top-down order
 722     if (hasAlpha)
 723     {
 724         hdr[HDR_ORIENTATION] |= 8; // number of alpha bits
 725     }
 726
 727     if ( !stream->Write(hdr, HDR_SIZE) )
 728     {
 729         return wxTGA_IOERR;
 730     }
 731
 732
 733     // Write image data, converting RGB to BGR and adding alpha if applicable
 734
 735     unsigned char *src = image.GetData();
 736     unsigned char *alpha = image.GetAlpha();
 737     for (int y = 0; y < size.y; ++y)
 738     {
 739         unsigned char *dst = scanlineData;
 740         for (int x = 0; x < size.x; ++x)
 741         {
 742             dst[0] = src[2];
 743             dst[1] = src[1];
 744             dst[2] = src[0];
 745             if (alpha)
 746             {
 747                 dst[3] = *(alpha++);
 748             }
 749             src += 3;
 750             dst += bytesPerPixel;
 751         }
 752         if ( !stream->Write(scanlineData, scanlineSize) )
 753         {
 754             return wxTGA_IOERR;
 755         }
 756     }
 757
 758     return wxTGA_OK;
 759 }
 760
 761 // ----------------------------------------------------------------------------
 762 // wxTGAHandler
 763 // ----------------------------------------------------------------------------
 764
 765 bool wxTGAHandler::LoadFile(wxImage* image,
 766                             wxInputStream& stream,
 767                             bool verbose,
 768                             int WXUNUSED(index))
 769 {
 770     if ( !CanRead(stream) )
 771     {
 772         if ( verbose )
 773         {
 774             wxLogError(wxT("TGA: this is not a TGA file."));
 775         }
 776
 777         return false;
 778     }
 779
 780     image->Destroy();
 781
 782     int error = ReadTGA(image, stream);
 783     if ( error != wxTGA_OK )
 784     {
 785         if ( verbose )
 786         {
 787             switch ( error )
 788             {
 789                 case wxTGA_INVFORMAT:
 790                     wxLogError(wxT("TGA: image format unsupported."));
 791                     break;
 792
 793                 case wxTGA_MEMERR:
 794                     wxLogError(wxT("TGA: couldn't allocate memory."));
 795                     break;
 796
 797                 case wxTGA_IOERR:
 798                     wxLogError(wxT("TGA: couldn't read image data."));
 799                     break;
 800
 801                 default:
 802                     wxLogError(wxT("TGA: unknown error!"));
 803             }
 804         }
 805
 806         image->Destroy();
 807
 808         return false;
 809     }
 810
 811     return true;
 812 }
 813
 814 bool wxTGAHandler::SaveFile(wxImage* image, wxOutputStream& stream, bool verbose)
 815 {
 816     int error = SaveTGA(*image, &stream);
 817
 818     if ( error != wxTGA_OK )
 819     {
 820         if ( verbose )
 821         {
 822             switch ( error )
 823             {
 824                 case wxTGA_MEMERR:
 825                     wxLogError(wxT("TGA: couldn't allocate memory."));
 826                     break;
 827
 828                 case wxTGA_IOERR:
 829                     wxLogError(wxT("TGA: couldn't write image data."));
 830                     break;
 831
 832                 default:
 833                     wxLogError(wxT("TGA: unknown error!"));
 834             }
 835         }
 836
 837         return false;
 838     }
 839
 840     return true;
 841 }
 842
 843 bool wxTGAHandler::DoCanRead(wxInputStream& stream)
 844 {
 845     // read the fixed-size TGA headers
 846     unsigned char hdr[HDR_SIZE];
 847     stream.Read(hdr, HDR_SIZE);     // it's ok to modify the stream position here
 848
 849     // Check whether we can read the file or not.
 850
 851     short colorType = hdr[HDR_COLORTYPE];
 852     if ( colorType != wxTGA_UNMAPPED && colorType != wxTGA_MAPPED )
 853     {
 854         return false;
 855     }
 856
 857     short imageType = hdr[HDR_IMAGETYPE];
 858     if ( imageType == 0 || imageType == 32 || imageType == 33 )
 859     {
 860         return false;
 861     }
 862
 863     short bpp = hdr[HDR_BPP];
 864     if ( bpp != 8 && bpp != 16 && bpp != 24 && bpp != 32 )
 865     {
 866         return false;
 867     }
 868
 869     return true;
 870 }
 871
 872 #endif // wxUSE_STREAMS
 873
 874 #endif // wxUSE_IMAGE && wxUSE_TGA