Algorithm 1 The polygon-based PA-NMS algorithm

Input:$B=[p_1,\dots p_n],S=[s_1,\dots s_n],D=[d_1,\dots d_n],N_t$ B is the list of initial polygon boxes S is the list containing corresponding detection scores D is the list of corresponding detection densities $N_t$ is the initial threshold $F=\left[\right]$ while $B!=\left[\right]$:        m argmax(S)        $M=B\left[m\right]$        $N_M$ = max $(N_t,d_M)$        F.append(M)        B.remove(M)        for p in B:               if polygon_IoU $(M,p)>=N_M$                   $B.$ remove(p)                   $S.$ remove(s) return $F,S$