OpenColorIO Alpha channel should be 1 by default, rather than 0

Currently if you make an apply call with a source ImageDesc that is RGB and a destination that is RGBA, the A value of the destination is 0. This is inconvenient since most clients will need to then set the alpha channel to 1 to make the image visible.

The proposal is that the alpha channel input value should start out as 1 in this scenario.

This would go into OCIO 2.3 to avoid changing behavior of the 2.2.x branch.

Mar 22 '23 18:03 doug-walker

I would be interested in taking a look at this issue for aswf devdays!

Oct 12 '23 05:10 royashams

Hi @doug-walker , Is there a sample test case that exists already that has destination RGBA and shows the issue where alpha is 0? Thank you!

Jul 26 '24 04:07 pennelee

Any CPUProcessor that starts with RGB input and produces RGBA output will have the A set to 0. You could start with a ColorSpaceTransform between any two color spaces to generate the Processor.

Jul 26 '24 05:07 doug-walker