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