OK, Luminosity Masks let us work on an image via different levels of density (nine levels with the Pat David/Saul Goode tool). Other than Decompose, is there a way to do something similar with color? The gradation of colors is on a continuous spectrum much like luminosity. I’d be curious to see if that was practical.
You can do this pretty easily in darktable using the masking features with the Tone Curve. The A and B channels in LAB can isolate color pretty well, I think.
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Technically you should be able to decompose an image to channels, and work with lum masks on specific channels as well. Though there wouldn’t be good real-time feedback in 2.8 at the moment. (I haven’t considered doing this directly on channels yet).
The closest thing I can think of is G’MIC’s command -split_colors. There is a GUI version of it in GIMP:
Filters → G’MIC → Layers → Colors to layers
I would start with these settings:
Changes to the Color tolerance setting may be slow, so start adjusting the other settings first. Of course, you would need to modify this to make it more like what you would expect from luminosity masking.
PS Curves in Darktable or RawTherapee would probably be the easier approach.
Definitely an easy task in darktable. Almost every module supports parametric masks which can create based on Luminosity, Hue, Saturation, LAB and grey scale depending on the module. You can then combine the different metrics (ie: hue and saturation) and apply the mask with a brush, shape or path if you want. Again, this is available for almost every adjust you want to make.
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I’ll definitely check that out–thanks!
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