Colormap Designer - Build a Colormap and See What It Costs

The published colormaps are a solved problem: viridis, the Crameri family and the Kovesi set are all better than anything you will draw by hand. The unsolved case is the constrained one, where the colours are partly given to you, the background is not negotiable, or the quantity is an angle and there is no correct answer at all. Give this page some colours, pick the suggestion you like, and read the damage report next to it.

• You give it colours and it gives you finished maps. A dozen candidates per run for sequential, fewer where the colours genuinely do not allow that many different ones, and the count says so instead of padding the list with near duplicates.
• Three families: sequential, diverging and cyclic. Both lightness directions are offered, because neither is correct in general: the ColorBrewer scales run light to dark and the perceptually uniform ones run the other way.
• Everything is computed in OKLab, and the ramp is reparametrised by arc length, so equal steps in the data are equal perceptual steps in the colours.
• The chroma ceiling is found before the curve is committed to and scales the whole profile, rather than clipping each point against the sRGB hull and flattening the designed shape into a plateau.
• The diagnostics show the five energy terms separately and not only their sum, because a sum cannot tell you which of your choices cost what.
• The lightness of the ramp is read back out of the emitted 8-bit values, not off the ideal curve, because uniformity is a property of the colours you actually see.
• Everything runs in your browser, with no data leaving it.