Algorithm 3 Determining the Edge Points from Candidate Edge Points

Input: Candidate Edge Points$P_n(0<\mathrm{n}<\mathrm{N})$ Output: Edge Points$P_m$$(0<m<M)$ $While(P_n\ne \varphi )$    $If$$P_n(0<\mathrm{n}<\mathrm{N})$$\in$Candidate Edge Points     $If$$distance\left(P_n\right)<threshold$        $acc\_arc={\displaystyle \sum _{i=1}^{5}arc\left(P_n·P_i\right)}$, $P_i$ is the 5 nearest candidate edge points.            $If$ $acc\_arc<threshold$              $P_m$ = $P_n$              $m=m+1,$ $n=n+1$            $\begin{array}{cc}end& if\end{array}$     $\begin{array}{cc}end& if\end{array}$    $\begin{array}{cc}end& if\end{array}$ $\begin{array}{cc}end& while\end{array}$