White balance applied twice

[priort (Todd Prior)]

@afre

Keep in mind that they are in development and therefore incomplete.

I don’t think any major changes to CC or documents so its pretty complete IMO for that topic…
Even the introduction to the module now Nov 2020 is pretty clear and comprehensive…

Introducing color calibration module (formerly known as channel mixer rgb)

[Screenshot_20201109_024706] TL; DR : this is a full rewrite in clean unbounded RGB of the channel mixer in darktable. The old one had some computational mistakes in it, plus clipped RGB at 100%. This also introduces much requested normalization options, that will keep the sum of parameters to 1, trying to preserve – rougly – luminance (actually, perceptual luminance is much more than a simple sum of R + G + B, since it depends on hue, but… TL; DR). Ok. But it’s named color calibration becaus…