docs: public static <T extends ImageGray<T>>T average( ImageMultiBand input , T output ) {
  		if( input instanceof Planar ) {
  			return (T)average((Planar)input,output);
  		} else if( input instanceof ImageInterleaved ) {
  			return (T)average((ImageInterleaved)input,output);
  		} else {
  			throw new RuntimeException("Unknown multiband image");
  		}
  	}