That's very interesting, thank you. Do you have examples of application of shaders in Jogamp Ardor3D based applications so I can study up?
However, my interest in BGR, RGB is that I don't want to expand the final image by 1 1/3 in a situation where
alpha is truly constant - it's a common use case for us and we often have long sequences of imagery to animate.
Actually, maybe it isn't. If the storage is aligned on 32 bits in memory, using one more byte to store a color component won't be a resource hit.
You just need a very basic fragment shader in which you pass the alpha component, the sampler for the texture and the texture coordinates in input and you modify the alpha component of the color in output. You may have to enable the blending.