color-math/src/ColorScale.js

expressions to manipulate colors

const Chroma = require('chroma-js')

export default class ColorScale {
  constructor(name, params, scaleParams) {
    this.name = name.toLowerCase()
    this.params = params || []
    this.scaleParams = scaleParams || []
  }

  toString() {
    return `<colorScale.${this.name}>`
  }

  clone() {
    const obj = new ColorScale(this.name, this.params.slice(0), this.scaleParams.slice(0))
    return obj
  }

  _getParamValue(params, name) {
    for (let i = 0; i < params.length; i++) {
      if (params[i].name === name) {return params[i].value}
    }
  }

  _applyParams(fn, params) {
    for (let i = 0; i < params.length; i++) {
      if (params[i].name !== 'colors') {fn = fn[params[i].name](params[i].value)}
    }
  }

  getFn() {
    const colors = this._getParamValue(this.scaleParams, 'colors')
    const ctor = Chroma[this.name]
    let fn = colors ? ctor(colors) : ctor()

    this._applyParams(fn, this.params)

    if (this.name !== 'scale') {fn = fn.scale()}

    this._applyParams(fn, this.scaleParams)

    return fn
  }
}