defining a left area and a right area respectively positioned on {HEAD ~ left and right sides} of {TAIL ~ the target pixel} on the line in the specified direction 
of
defining a left area and a right area respectively positioned on { HEAD ~ left and right sides } of { TAIL ~ the target pixel } on the line in the specified direction
OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH