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