ROC curves of the lens search method using both spatial extent and number of blobs. The subgroups of lensed quasars are the same as the subgroups in Fig. 6. The ROC curves are plotted by varying p_thrs% from 0% to 99.5% at N_thrs = 4 with the preselection on the number of blobs N_crit = 2. The crosses, triangles, and circles indicate the points on the ROC curves when p_thrs% = 0%,55%, and 75%, respectively. With the preselection N_crit = 2, our lens search algorithm could identify the bright lensed quasars with wide separation at (TPR, FPR) = (97.6%,2.6%), which is similar to the lens search performance when no preselection is performed. The ROC curves also start from a much lower FPR (crosses) with the preselection N_crit = 2. The ROC curves are zoomed-in with the FPR (x-axis) spanning from 0 to 0.05 in the small panel.