* @return array|WP_Error {'path'=>string, 'file'=>string, 'width'=>int, 'height'=>int, 'mime-type'=>string}
*/
public function save( $filename = null, $mime_type = null ) {
* @return array|WP_Error {'path'=>string, 'file'=>string, 'width'=>int, 'height'=>int, 'mime-type'=>string}
*/
public function save( $filename = null, $mime_type = null ) {