ColorThief\ColorThief::getColorIndex PHP Method

    public static function getColorIndex($red, $green, $blue, $sigBits = self::SIGBITS)
    {
        return ($red << 2 * $sigBits) + ($green << $sigBits) + $blue;
    }

 /**
  * @dataProvider provide5bitsColorIndex
  */
 public function testGetColorIndex5bits($r, $g, $b, $index)
 {
     $this->assertSame($index, ColorThief::getColorIndex($r, $g, $b));
 }