2001.07.20 16:52 "RE: LZW TIFFReadScanline woes", by Sean Finn

Sorry, I should have put this in the original question:

I have a routine that skips through the Tiff file, let's call it TSeek(int lines). It basically looks like this:

void TSeek(int lines)
{
  for(int i=0; i < lines; ++i)
  {
    // buf is a previously allocated 1-scanline size'd buffer
    TIFFReadScanlines(m_tif, buf, 1);
  }
}

This allows me to walk through the compressed file without worrying about random access. The sub-sampled images, on further inspection, seem to have a problem when the Strip changes. There is either a duplicated scanline or a missing one. My seek routine is the likely suspect, other than there are no problems using the same code in an uncompressed file.

I have a work-around of uncompressed the whole image into a local buffer, and then skipping around in that to retrieve my sub-sampling. This is fine (inefficient, but fine) until I get to a large file (we have a couple 60 MB).

Thanks for everyone's help,

Sean