Add cividis color scale, a scheme for viewers with color vision deficiency

[hollasch]

The cividis scale is a derivative of the viridis scale, adjusted for viewers with color vision deficiency, and also for those with standard vision, but avoiding the errors common with rainbow-style schemes.

References:

• 256-color LUT
• Scientific American article
• A Simulation Color Table for Engineers with Color Vision Deficiency
• Optimizing colormaps with consideration for color vision deficiency to enable accurate interpretation of scientific data

[mbostock]

Here’s a quick demo:

https://beta.observablehq.com/@mbostock/cividis

[hollasch]

Sweet! Wish I could have found a continuous formula, but the 256 LUT is probably fine. Looks great Mike.

[mbostock]

I computed a fifth-order polynomial regression as a continuous approximation that seems to work well. It’ll be in the next release.

[hollasch]

Thanks Mike!