2004.12.08 02:35 "[Tiff] Q: writing tiled TIFFs", by Chris Losinger

2004.12.09 13:38 "Re: [Tiff] Q: writing tiled TIFFs", by Chris Losinger

256x256 is apparently the LibTiff default. why does LibTiff choose that for a 200x200 image? i don't know.

How do you arrive at this 'LibTiff default'?

         // set image dims
      TIFFSetField(tiff, TIFFTAG_IMAGEWIDTH, (uint32) nWidth);
      TIFFSetField(tiff, TIFFTAG_IMAGELENGTH, (uint32) nHeight);

         // get default tile size
       uint32 tilewidth, tileheight;
       tilewidth = 0;
       tileheight = 0;
       TIFFDefaultTileSize(tiff, &tilewidth, &tileheight);

         // use that size
       TIFFSetField(tiff, TIFFTAG_TILEWIDTH, tilewidth);
       TIFFSetField(tiff, TIFFTAG_TILELENGTH, tileheight);

I generally decide on the tile size myself, and set TIFFTAG_TILEWIDTH and TIFFTAG_TILELENGTH tags before using the actual raster write functions. Are you doing that?

no, because i assumed LibTiff would generate a reasonable default tile size, similar to the way it generates reasonable default strip sizes.

If not, perhaps you should try that and see if it solves your problem. If you are doing that, or if it doesn't solve your problem, perhaps you could post a code snippet, then maybe we'll be able to see what's going on.

the image i'm using is 8 bits per pixel.

the tile setup part is above. the actual tile writing part looks like this:

         // need a single tile to hold a copy of the source data
       TIFFGetField(pCTIS->tiff, TIFFTAG_TILELENGTH, &th);
       TIFFGetField(pCTIS->tiff, TIFFTAG_TILEWIDTH, &tw);

       ISByteArray tempTile;
       if (tempTile.GetPtr() == NULL)
          return IS_ERR_MEM;

       for (UINT32 y = 0; y < nHeight; y+=th)
          for (UINT32 x = 0; x < nWidth; x+=tw)
             // copy a square part of the source image (or as much of it as we can)
             // to the tile buffer.
             CISOverlay io;
                io.OverlayImage(tempTile, tw, th,        // output
                   pImg, nWidth, nHeight,                // input (250x200, in this case)
                   -x, -y,                               // position the source image 'over' the tile buffer
                   1.0, pCTIS->bitDepth / 8,
                   TIFFTileRowSize(pCTIS->tiff),         // number of bytes in tile buffer row
                 rowStride,                      // number of bytes in source image row

             if (TIFFWriteTile(pCTIS->tiff, tempTile.GetPtr(), x, y, 0, 0) == -1)
                return FALSE;

Chris Losinger
smallest@smalleranimals.com          http://www.smalleranimals.com