* Merge a parameter array into a string appropriate for inclusion in filenames
*
* @param $params array Array of parameters that have been through normaliseParams.
+ * @return String
*/
abstract function makeParamString( $params );
/**
* Parse a param string made with makeParamString back into an array
*
- * @param $str string
+ * @param $str string The parameter string without file name (e.g. 122px)
+ * @return Array|Boolean Array of parameters or false on failure.
*/
abstract function parseParamString( $str );