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