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August 2007
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2007.08.06 22:48 "Re: Transparency ... associated or unassociated alpha is morecompatible?", by Bob Friesenhahn
On Mon, 6 Aug 2007, Chris Cox wrote: > PNG and SGI RGB support associated alpha (aka transparency), just not premultiplied. Thanks for correcting my wrong use of terms. It is a pity that TIFF does not provide a way to specify associated alpha which is not premultiplied. > TGA is supposed to support associated alpha (transparency), but most > users of TGA don't seem to understand the difference and get > transparency and general (unassociated) alpha channels confused. > When Photoshop 7 shipped with transparency support in TGA format, > the users got so confused that Adobe had to go back to using > unassociated alpha. The TGA users still can't agree on what they > want, much less what they understand. That is interesting to know. As far as I am aware, GraphicsMagick handles alpha correctly (according to written specification) for TGA files. I spent quite a bit of time double checking it and fixing things. Bob ====================================== Bob Friesenhahn bfriesen@simple.dallas.tx.us, http://www.simplesystems.org/users/bfriesen/ GraphicsMagick Maintainer, http://www.GraphicsMagick.org/