On Sun, 11 Nov 2001 08:02:17 -0500, John David Haiducek
<jha### [at] enginumichedu> wrote:

>I had thought that Photoshop's "Lighten" mode did addition. Am I wrong
>about that?

If layer A is above layer B, then for a pixel [x,y]:

f_lighten(A,B,[x,y]) = (lum(A,[x,y])>lum(B,[x,y]))?A[x,y]:B[x,y]

If you want to do addition, try screen mode or image/channel
composition.


Peter Popov ICQ : 15002700
Personal e-mail : pet### [at] vipbg
TAG      e-mail : pet### [at] tagpovrayorg

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