Generate LUT from swatches?

[Iain]

Customize CLUT in G'MIC

I just discovered “Customize CLUT” filter in the GMIC and played with it a bit. I immediately noticed that is a very powerful tool for color manipulation of photos. The ability to quickly and accurately replace a color with another opens a wide range of possibilities to change photos stylistically. What would make this filter even more powerful would be the possibility to replace a color with transparency - to be able to choose alpha channel as target color. Is this possible?