colorjs.io/src/distance.js

Let’s get serious about color

import ColorSpace from "./space.js";

/**
 * Euclidean distance of colors in an arbitrary color space
 */
export default function distance (color1, color2, space = "lab") {
	space = ColorSpace.get(space);

	// Assume getColor() is called on color in space.from()
	let coords1 = space.from(color1);
	let coords2 = space.from(color2);

	return Math.sqrt(coords1.reduce((acc, c1, i) => {
		let c2 = coords2[i];
		if (isNaN(c1) || isNaN(c2)) {
			return acc;
		}

		return acc + (c2 - c1) ** 2;
	}, 0));
}