this implements the popular and simple lift gamma gain scheme to colour grade images.
note that it works in rgb and may result in out of gamut/spectral locus colours.
this is in fact using the ACES colour decision list (CDL) formula for slope/offset/power but i didn't rename the parameters because it's so similar. also this does not work in log space nor in ACEScc colour space, so in a way it's different anyways.
see: ACES S-2016-001 : ACEScct --- A Quasi-Logarithmic Encoding of ACES Data for use within Color Grading Systems
lift a 3-vector for red green blue to lift the blacksgamma a 3-vector for red green blue to push the gamma (affects the mid tones mostly)gain a 3-vector for red green blue gain. this affects the whole image (but mostly pins the highlights) and works as rgb white balance coefficients would.