{HEAD ~ The method} 19 wherein the function is a logical function including the minimum or maximum of {TAIL ~ the height and gray scale values} 
{ HEAD ~ The method } 19 wherein the function is a logical function including the minimum or maximum of { TAIL ~ the height and gray scale values }
HEAD HEAD HEAD HEAD HEAD HEAD OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL