Add CMY color space

[karenbennett]

Cyan, magenta, and yellow, the pigment primaries, are complements of the light primaries, red, green, and blue, respectively. Would it be possible to add the CMY color space?

[Artoria2e5]

• There is no single CMY color space; any combination of ink, process, and paper creates a new one.
• Going from RGB to any particular CMY(K) color space is very much non-trivial.

[Artoria2e5]

That said, since there is support for a very naive version of CMYK, it only makes sense to make an equally naive version of CMY or to remove them both. For now you can use:

cmyk2cmy = function(cmyk) {
  const [c, m, y, k] = cmyk
  return [c + k, m + k, y + k]
}
cmy2cmyk = function(cmy) {
  const [c, m, y] = cmy
  const k = Math.max(...cmy)
  return [c - k, m - k, y - k, k]
}

const chroma = require('chroma-js')
const Color = chroma('black').__proto__ // big hack
Color.prototype.cmy = function() { cmyk2cmy(this.cmyk()); }
chroma.cmy = (...args) => new Color(...cmy2cmyk(args), 'cmyk')