public function assertImageSimilarity($image1, $image2, $threshold = 0, $message = 'Images are not within similarity threshold.')
    {
        $image1 = $this->initImage($image1);
        $image2 = $this->initImage($image2);

        $this->assertLessThanOrEqual($threshold, $this->performCompare($image1, $image2), $message);
    }