2010.06.12 17:01 "Re: [Tiff] Class Y (YCbCr) tiffs with 420 subsampling", by Bob Friesenhahn

Sure enough, however, I'm not quite clear on the semantics of TIFFScanlineSize(). Actually, if you do have subsampling, what is the the "size" of "a" scan line given that every other scanline holds only a subset of all samples? This is not at all clear.

Given this problem, I'm not sure whether the bug is in TIFFScanlineSize() or in the directory reader.

It may be that using scanline access is quite wrong for your subsampled files. It is not possible to support vertical sampling in a scanline. The data is stored using strips (which support multiple scanlines and can support vertical sampling) so it seems that TIFFStripSize() should be used rather than TIFFScanlineSize() and the strip should be read as a whole.

Bob
--
Bob Friesenhahn
bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/