public function thumb($url, $width, $height = null)
    {
        return $this->resize($url, $width, $height, true);
    }
public function thumb($url, $width, $height = null)
    {
        return $this->resize($url, $width, $height, true);
    }
public function thumb ( $ url , $ width , $ height = null ) { return $ this -> resize ( $ url , $ width , $ height , true ) ; }
Helper for creating thumbs
@param string $url
@param integer $width
@param integer $height
@return string
Helper for creating thumbs