plotboilerplate/src/ts/utils/algorithms/getContrastColor.ts

A simple javascript plotting boilerplate for 2d stuff.

/**
 * @author Original from Martin Sojka. Ported to TypesScript by Ikaros Kappler
 * @date   2020-11-10
 */

import { Color } from "../datastructures/Color";

const BLACK = Color.makeRGB(0, 0, 0);
const WHITE = Color.makeRGB(255, 255, 255);

/**
 * Contrast color algorithm by Martin Sojka's.
 * Found at
 *    https://gamedev.stackexchange.com/questions/38536/given-a-rgb-color-x-how-to-find-the-most-contrasting-color-y/38542#38542
 *
 * @requires Color
 */
export const getContrastColor = (color: Color): Color => {
  // r,g,b in [0..1]
  const gamma: number = 2.2;
  const L: number = 0.2126 * Math.pow(color.r, gamma) + 0.7152 * Math.pow(color.g, gamma) + 0.0722 * Math.pow(color.b, gamma);
  const use_black: boolean = L > Math.pow(0.5, gamma);
  return use_black ? BLACK : WHITE;
};