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April 2009
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2009.04.27 20:32 "Re: Question regarding unassociated alpha", by Amir Ebrahimi
On Apr 27, 2009, at 1:26 PM, Edward Lam wrote: > > Probably a bug. > > This code only gets used in the high-level libtiff > TIFFReadRGBAImage() interfaces. Given that it's supposed to do all > sorts of conversions for you, I think it's semantically supposed to > always return pre-multiplied alpha images. Reading the code, it > leaves the RGB components alone when reading an associated alpha > tiff, and multiplies in the alpha for unassociated alpha tiff files. > > Given that this code was originally developed on SGIs, the norm back > then was probably to use premultiplied alpha. ie. influenced by > Duff's Compositing Digital Images paper. > > http://keithp.com/~keithp/porterduff/p253-porter.pdf Okay, so maybe a conditional define or read option is due? :: Amir Ebrahimi :: Developer @ Unity Technologies www.unity3d.com