d3plus-color/es/src/contrast.js

Color functions that extent the ability of d3-color.

import { getColor } from "./defaults.js";
import { rgb } from "d3-color";

/**
    @function colorContrast
    @desc A set of default color values used when assigning colors based on data.
    @param {String} c A valid CSS color string.
    @param {Object} [u = defaults] An object containing overrides of the default colors.
    @returns {String}
*/
export default function (c) {
  var u = arguments.length > 1 && arguments[1] !== undefined ? arguments[1] : {};
  c = rgb(c);
  var yiq = (c.r * 299 + c.g * 587 + c.b * 114) / 1000;
  return yiq >= 128 ? getColor("dark", u) : getColor("light", u);
}