AWARE SYSTEMS
TIFF and LibTiff Mail List Archive

Thread

2010.06.11 21:39 "[Tiff] Class Y images with alpha channels", by Thomas Richter
2010.06.11 23:26 "Re: [Tiff] Class Y images with alpha channels", by Bob Friesenhahn
2010.06.14 05:59 "Re: [Tiff] Class Y images with alpha channels", by
2010.06.14 06:36 "Re: [Tiff] Class Y images with alpha channels", by Thomas Richter
2010.06.14 07:51 "Re: [Tiff] Class Y images with alpha channels", by
2010.06.14 14:57 "Re: [Tiff] Class Y images with alpha channels", by Bob Friesenhahn

2010.06.11 23:26 "Re: [Tiff] Class Y images with alpha channels", by Bob Friesenhahn

is there a possibility to add an alpha channel to a class Y (YCbCr) tiff image? I don't see this in the rev.6 specs.

You could add an alpha channel as an extra sample or a fourth plane in a planar TIFF, but since the specification does not mention doing this, perhaps only your own application could make sense of it. I think that using planar TIFF is safest since readers can skip reading the last plane and still return the YCbCr image, but not many readers support planar (separated) TIFF.

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