It is true that the end points lose the darkest and lightest shades -- this is another point I was too lazy to addres, but assumed you could rectify this. That source image only has 200 unique colors in it, and a lot of them are non-gold shades of gray -- this image does not contain a rich color selection -- so interpolation into absent colors is necessary. And your first point (undesired patterns of brightness density) would be addressed by using brightness levels, instead of the densities of unique colors at a similar brightness, to group the "reference" colors (which I was also too lazy to do here).

In reply to Re^3: A data selection problem(in3D). by coicles
in thread A data selection problem(in3D). by BrowserUk

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