defining {HEAD ~ a partial image} in {TAIL ~ the specified area}, the partial image being composed of a target pixel and peripheral pixels on a line in a specified direction in which the target pixel exists 
in
defining { HEAD ~ a partial image } in { TAIL ~ the specified area } , the partial image being composed of a target pixel and peripheral pixels on a line in a specified direction in which the target pixel exists
OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH