Color RGB matcher

Color.php

<?php

class Color
{
	private $hex;
	private $r;
	private $g;
	private $b;
	
	public function __construct(string $hex) {
		$this->hex = ltrim($hex, '#');
		[$this->r, $this->g, $this->b] = self::makeRGB($this->hex);
	}
	
	public function r(): int {
		return $this->r;
	}
	
	public function g(): int {
		return $this->g;
	}
	
	public function b(): int {
		return $this->b;
	}
	
	private static function makeRGB(string $hex): array {
		return [
			hexdec(substr($hex, 0, 2)),
			hexdec(substr($hex, 2, 2)),
			hexdec(substr($hex, 4, 2)),
		];
	}
	
	// @see https://stackoverflow.com/a/9085524/443479
	public function distanceFrom(Color $color): float {
		$rMean = ($this->r + $color->r()) / 2;
		$r = $this->r - $color->r();
		$g = $this->g - $color->g();
		$b = $this->b - $color->b();
		return sqrt((((512+$rMean)*$r*$r)>>8) + 4*$g*$g + (((767-$rMean)*$b*$b)>>8));
	}
	
	public function __toString(): string {
		return "#" . $this->hex;
	}
}