>It depends on what you are doing weather pre multiplied alpha is useful
>or not.  For compositing and image warping pre multiplied alpha is great.  for
>color correction pre-multiplied alpha just gets in the way.  Since
>pre-multiplying the alpha does throw away a few bits of information my
>preference is for non-pre-multiplied alpha.

I know 3D software that outputs pre or non-pre, user selectable, but read
only pre. The manual says all that, and recommends non-pre for "drawing

What I do not understand, is why I would like pre for compositing? If I have
an image with pre, when I composite with another image, I will get damaged
borders, instead of true composition based in the alpha, no? If software
knows it, it can be fixed... but after lossing precission, no?


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