public function pngToWbmp(String $pngFile, String $wbmpFile, Array $settings = []) : Bool
    {
        if( is_file($pngFile) )
        {
            $height    = $settings['height']    ?? 0;
            $width     = $settings['width']     ?? 0;
            $threshold = $settings['threshold'] ?? 0;

            return png2wbmp($pngFile, $wbmpFile, $height, $width, $threshold);
        }
        else
        {
            return false;
        }
    }