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2008.04.17 21:48 "Re: a question about creating transparency of the image in TIFF", by Bob Friesenhahn
On Thu, 17 Apr 2008, Chris Cox wrote: > There are 2 types of alpha in TIFF: associated (transparency) and > unassociated (undefined extra channels). > > Also, the TIFF spec. states that images with associated alpha (transparency) > must be premultiplied. The TIFF specification does not prevent a colormapped file with transparency but the colors in the colormap would then need to be premultiplied, which could be a challenge to surmount. As a result, no one does this. Popular software like Photoshop does not place any interpretation on unassociated alpha, so such channels are just "extra" channels that only a Photoshop expert could figure out. Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/