[cairo] Compositing / blend functions documentation
Bill Spitzak
spitzak at d2.com
Tue Jan 25 16:46:54 PST 2005
Note that the Delphi document has got "A" and "B" swapped from the SVG
and most other documentation.
Bill Spitzak wrote:
> Carl asked me where what documentation we had on blend functions.
> I asked around here for where we got the math and was pointed at this page:
>
> http://www.pegtop.net/delphi/blendmodes/
>
> and also at the page Carl already referenced:
>
> http://www.w3.org/TR/SVG12/rendering.html
>
> The SVG page describes the full functions including the effect of alpha.
> The Delphi page ignores the alpha, but the functions can be converted:
> if the simple function is F(A,B) and the alphas are a,b, the new
> function is F(A/a,B/b)*ab+A(1-b)+B(1-a).
>
> I think the Delphi page has some simpler and more likely functions for
> some things, in particular softlight. It looks to me like the SVG guys
> tried to figure out the function by testing it in PDF/Photoshop and
> arrived at much more complex functions than necessary.
>
> _______________________________________________
> cairo mailing list
> cairo at cairographics.org
> http://lists.freedesktop.org/mailman/listinfo/cairo
>
>
More information about the cairo
mailing list