Removing white premultiplication?

[Hugh]

Not the nicest of things to work with, but easily fixable...

Create a white solid using a Color node (white colour, but 0 in the alpha)

Create an Outside node. Plug the white colour into the first input, and your image (with alpha) into the second input.

Then create an ISub node - plug your image (on white) into the first input, and the result of the Outside node into the second.

Your result will be your image on black.

If you don't believe me that this will work, here's a faked-up example:

Color1 = Color(500, 500, 1, 1, red, red, 0, 0);
ColorWheel1 = ColorWheel(500, 500, 1, 0, 1, 1, 1);
Blur52 = Blur(ColorWheel1, 90, xPixels/GetDefaultAspect(), 0,
"gauss", xFilter, "rgba");
Over10 = Over(Blur52, Color1, 1, 0, 0);
Outside19 = Outside(Color1, Over10, 1);
ISub5 = ISub(Over10, Outside19, 1, 100);


In this, the result of the Over is effectively what you've got to begin with.

[StefanAlbertz]

Thank you, Hugh!! Solved my problem :)

[beaker]

also there is an aepremult macro on highend3d that fixes any AE images that are premultipled by anything other then black. Though it probably does the same thing that Hugh's script does.

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