Hi,
Thanks for answering.
Looking at posts regarding your quantizer, I got the impression that it reduced to a determined amount of colors i.e 256 colors. In my ambition to extract elevation curves, mentioned in my first post, I think I might need to try different numbers of colors in the resultant image. Have read your tutorials on BGRABitmap(excellant), but about the quantizer I didn't find too much. Perhaps I'm just too stupid to understand how to use it to it's full potential.