Annotation tool color picker not sampling in linear space when using OCIO

[markreidvfx]

Currently the annotation tool's color picker samples pixel values after the display transform has been applied with glReadPixels. When you draw and are using OCIO, the color you sample will appear wrong because the OCIODisplay gets applied a second time. This is because the RV paint node is placed between the OCIOFile and OCIODisplay transforms in the node graph.

2024-03-11.13-28-11.mp4

Is there a way or can we add a way to sample a pixel's linear value, preferably after the paint node. How about being able to do it at any arbitrary place in the node graph too? I assume it hasn't been done because everything is in the gpu at this point and it would require rendering/sync to cpu visible buffer.

I've worked around this internally by using sourcePixelValue to get the raw pixel value. Then I applied the same OCIOFIle transform via OCIO's python api. This unfortunately doesn't let you sample from previously painted brush strokes. I consider reversing the display lut but then I'd also have to consider the other effects (like exposure, saturation) applied to the linear image.