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2005.06.07 18:43 "Group4 compression & alpha channel", by Bob Friesenhahn
2005.06.07 19:15 "Re: Group4 compression & alpha channel", by Andrey Kiselev
2005.06.07 19:29 "Re: Group4 compression & alpha channel", by Bob Friesenhahn

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/