mattdesl

It may be of interest to some game/graphics devs here...

PS: worth mentioning the RGB to CMYK function credited to me is not my original work, I believe I got it off stack overflow or similar many years ago. A more robust way of doing this transformation would be with a color management system and profile, as it happens I’ve done a bit of work on that! [1] Used this here [2].

Transforming with ICC profile will give you a result that might be closer to how a screen printer would turn your digital image into a four colour print, but more advanced screen printing workflows these days tend to use “rip” software that handles many layers (eg: 12 colors instead of 4) and stochastic screening [3] which produces quite different results than what most halftone shaders are doing.

Sketch synthesis is an area I'm pretty interested in lately; I'm currently exploring similar things with CLIP to guide fitness, natural evolution strategy to optimize the rendered results, and using an implicit neural representation to represent pen plotter paths (rather than a series of explicit curves/strokes).[2]

And I think you might be mis-remembering Ottosson's original blog post; he demonstrates a gradient between white and blue, not blue and yellow.

- what works well for this image might not work well for other images! I learned the hard way after lots of testing on this image, only to find things that did not generalize well.

- parametrizing the AB plane weight is pretty useful for color quantization; I’ve found some images will be best with more weight given to colour, and other images need more weight given to tone. OKLab creator suggests a factor of 2 in deltaEOK[1] but again this is something that should be adjustable IMHO..

- there’s another interesting and efficient color space (poorly named) sUCS and sCAM[2] that boasts impressive results in their paper for tasks like this. Although I’ve found it not much better for my needs than OKLab in my brief tests[3] (and note, both color spaces are derived using CIEDE2000)