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