protected function createTransparentImage($width, $height)
    {
        $image = @imagecreatetruecolor($width, $height);
        if (!$image) {
            throw new \Exception('Missing libgd support');
        }
        imagealphablending($image, false);
        $transparency = $this->transparentColor($image);
        imagefill($image, 0, 0, $transparency);
        imagecolordeallocate($image, $transparency);
        imagesavealpha($image, true);
        return $image;
    }