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Date: Fri, 11 Jun 2010 18:26:11 -0500 (CDT)
From: Bob Friesenhahn <bfriesen@simple.dallas.tx.us>
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To: Thomas Richter <thor@math.tu-berlin.de>
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Cc: tiff@lists.maptools.org
Subject: Re: [Tiff] Class Y images with alpha channels
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On Fri, 11 Jun 2010, Thomas Richter wrote:

> Hi folks,
>
> 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/
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