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