isDarkColor.ts

import hexRgb from "hex-rgb";

// see: https://www.w3.org/TR/WCAG20/#relativeluminancedef
export function isDarkColor(hexColor: string): boolean {
  const { red, green, blue } = hexRgb(hexColor);

  const [r, g, b] = [red / 255, green / 255, blue / 255].map((v) =>
    v <= 0.03928 ? v / 12.92 : Math.pow((v + 0.055) / 1.055, 2.4)
  );

  const luminance = 0.2126 * r + 0.7152 * g + 0.0722 * b;

  return luminance <= 0.179;
}