After the other thread mentioning linear vs sRGB gamma it occurs that actually some possibilities are missing for channel selection (i.e. the -ac command).

We can already choose linear RGB, but what about linear YCbCr? I believe G’MIC -rgb2ycbcr is “Y’CbCr from R’G’B’”, in other words luma is still gamma compressed. It’s not commutative either (sRGB -> RGB must be done after RGB -> Y’CbCr). I haven’t considered other transforms, but for things such as HSV perhaps it’s less important because it’s commutative then.