This patch removes the Premultiplied option from the Alpha Over node.
The reasoning is as follows:
- The option mixed between alpha being straight and premultiplied, a
state which doesn't happen in practice.
- The option conflicts with the Convert Premultiplied option, if it is
not zero, then Convert Premultiplied does nothing.
- The option is implemented in a lossy way. It premultiplies the alpha
assuming it is straight, then converts the result to straight again,
then mixed between both results. This is as opposed to mixing the
original straight input with the premultiplied input. The successive
alpha conversion causes data loss in transparent regions.
Pull Request: https://projects.blender.org/blender/blender/pulls/138428
ebe67e5ca0