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