This patch removes the Convert Premultiplied option from the Brightness
and Contrast node. The reasoning is that it is the only node that has
the option to operate on straight alpha, while not being particularly
different. Adding alpha conversion nodes around it is also very easy.
Furthermore, alpha conversion is a lossy operation, so the option looses
data in emissive pixels, and since it is enabled by default, users not
familiar with the exact mechanism of the option wouldn't know how to fix
this.
Pull Request: https://projects.blender.org/blender/blender/pulls/138318
92ac9f3b25