I would like to introduce an experimental feature I’m working on : color-matching pictures.
It comes from the fact that, even with top-notch color science and using pictures shot in seemingly similar conditions, light may change during a shooting session. As a result, it may prove difficult to obtain a consistent look across pictures, because copy-pasting the history will yield slightly different results. When you have a secondary color-grading (set in color balance RGB or RGB curves), you don’t really to want fine-tune it on a per-image basis, because that will take forever. Instead, you want to adjust the illuminant and the exposure, that is chromaticity and brightness, because in theory, that will normalize all pictures to the same ground through (taking light variations into account), which in theory, should help color balance RGB to produce the same effect.
Notice, though, that “same effect” ≠ same look, because human vision is sensible to contrast and to surround, so ensuring the the same output colors is not enough to ensure the same overall perception (if, for example, one pic has 1/3 of bright sky and 2/3 of dark ground, and another has the opposite, the change in background will affect the perception of the subject in the foreground).
In any case, I recorded a video to show how to use it, and the code is on Github and working:
This also enables to match skin tones to an arbitrary hue, an use case I don’t endorse, but you take responsibility for the social consequences of your actions.