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March 2005
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2005.03.17 10:47 "Photoshop Masked area TIFF images", by <mg76@inwind.it>
Hi, I'm dealing with tiff photoshop images with extra channels. Usingg tifflib I'v got the dat relative to extra channels kept in Photoshop Tag. Now I'd like to know how is obtained the resulting color of the final pixel deriving from a background pixel with a Mask areas Photoshop extra channel . For example, if I have an RGB pixel A (255 255 255 0) and a mask of color (255 0 0 )with opacity 0.75 I get as a resulting pixel after compositing: P(255 137 137). How? Given a pixel A(r,g,b,0) and a mask color C(r1,g1,b1) with opacity x, what is the resulting pixel after compositing? The compositing formula pixelOut[j] =((1/MAXVALUE)*((MAXVALUE-alphaValue)*q[j]+(1/MAXVALUE)*alphaValue*(MAXVALUE-betaValue)*p[j]))+0.5; does not work!!! Does anyone can help me??? Thanks Jade