Table 4.

Algorithm of two-sided pointwise surface distance (PSD) calculation

Input: Binary mask dataset of A, B.
Output: PSD(S(A), S(B))
1	S(A) = {a1, a2, …, an} ← Edge extraction of A;
2	S(B) = {b1, b2, …, bm} ← Edge extraction of B;
3	Compute one-sided PSD from A to B
4	for each Point a in S (A) do
5	d(a, S(B)) ← The minimum distance from a to S(B);
6	if a ∈ B then
7	α ← +1; //Overestimation of PSM
8	else a ∉ B then
9	α ← −1; //Underestimation of PSM
10	end if
11	dg(a, S(B)) ← α ⋅ d(a, S(B));
12	end for
13	$g\left(S\left(A\right),S\left(B\right)\right)\leftarrow \sum _{i=1}^n{d}_g\left(a,S\left(B\right)\right)/n;$
14	Compute one-sided PSD from B to A
15	for each Point b in S(B) do
16	d(b, S(A)) ← The minimum distance from b to S(A);
17	if b ∉ A then
18	β ← +1; //Overestimation of PSM
19	else b ∈ A then
20	β ← −1; //Underestimation of PSM
21	end if
22	dg(b, S(A)) ← β ⋅ d(b, S(A));
23	end for
24	$g\left(S\left(B\right),S\left(A\right)\right)\leftarrow \sum _{i=1}^m{d}_g\left(b,S\left(A\right)\right)/m;$
25	Compute two-sided PSD index of A and B
26	PSD(S(A), S(B)) ← 0.5 {g(S(A), S(B)) + (S(B), S(A))}
27	Return PSD(S(A), S(B));