afterUpload() protected method

The default implementation raises the [[EVENT_AFTER_UPLOAD]] event. You may override this method to do postprocessing after the file is uploaded. Make sure you call the parent implementation so that the event is raised properly.
protected afterUpload ( )
 /**
  * @inheritdoc
  */
 protected function afterUpload()
 {
     parent::afterUpload();
     if ($this->createThumbsOnSave == true) {
         $this->createThumbs();
     }
 }