On Dec 15, 2011 1:24 PM, "Jason van Gumster" <ja...@handturkeystudios.com> wrote:
> I understand the necessity/convenience of internally choosing one alpha format > over the other. However, I'm curious how this would impact saving to image > formats that only support one alpha format (e.g. premultiplied alpha is > explicitly not part of the PNG spec[1]). Granted, I could be missing something > and it's not a huge issue, but I figured it'd be worth asking. > A library like OIIO enforces an internal premultiplied format. All output is then subject to a divide for formats that require unassociated alpha. When doing an operation at 32 bit depth, the loss is considered negligible with respect to the gains of an internally consistent format. As noted by Brecht, the divide is mandatory for moving back and forth between linearization and non linear values. It would also be required to unassociate the alpha for any alpha channel manipulation such as math work. Bear in mind that most industrial grade formats permit either form of alpha, such as EXR. With respect, TJS _______________________________________________ Bf-committers mailing list Bf-committers@blender.org http://lists.blender.org/mailman/listinfo/bf-committers
