Let an ideal 2-D highpass filter $H(k, l)$ is defined between the limits $\{-4,-3$, $-2,-1,0,1,2,3\}$ in both the directions. Find the filter coefficients for a given cutoff radius $r$ such that $H(k, l)=1$ outside the circle defined by $r$ and zero elsewhere.
(i) $r=1$
(ii) $r=2$
(iii) $r=3$