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June 2005
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2005.06.07 19:29 "Re: Group4 compression & alpha channel", by Bob Friesenhahn
> > It has been observed that when GraphicsMagick writes a min-is-black > > TIFF image with Group4 compression and an alpha channel (as an extra > > sample) that the right half of the image is lost. The image > > description is: > > ... > > Are there any known issues in libtiff with this scenario? > > I do not remember any reports of such a bug. I think it is a matter for > our Bugzilla. Will do once I have spent more time on the issue. Before anyone should mention it, I certainly agree that storing the alpha channel as an extra 1-bit sample does not make much sense for FAX and group4 compression. It makes much more sense to save the alpha channel as a separate plane so it is easier to compress. Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/