EndStop4 computes end-stop activations: es := lsum - max(off) lsum is the length-sum activation to the "left" of feature and max(off) is the max of the off inhibitory region to the "right" of feature.

LenSum4 computes summed line activations.

end-stop off coordinates for 4 angles, also uses negated versions these go with the negative versions of Line4X (i.e., are in same dir) -- | = (1,1), (1,0), (1,-1) (X,Y) --| / = (0,1), (1,1), (1,0) --- | = (-1,1), (0,1), (1,1) \ = (0,-1), (1,-1), (1,0) --| 3 coords per angle.

linear neighbor coordinates for 4 angles, also uses negated version -- = (1,0) (X,Y) / = (1,1) | = (0,1) \ = (1,-1).