{HEAD ~ The value} of {TAIL ~ each local extremum pixel} is modified as a function of the current local reference point 
{ HEAD ~ The value } of { TAIL ~ each local extremum pixel } is modified as a function of the current local reference point
HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH