private function outputImage(string $imagePath = ''): void
    {
        $fPointer = \fopen($imagePath, 'rb');
        $this->sendCachingHeaders($imagePath);
        \header('Content-Type: '.$this->getImageContentType());
        \header('Content-Length: '.\filesize($imagePath));
        \fpassthru($fPointer);
        \fclose($fPointer);
        die();
    }