Algorithm 1 Overall Pipeline of DHV ROI Extraction

Require: A DHV image I and our detector D.

1: Feed I to D to obtain four keypoints P0, P1, P2, P3;

2: Set the line through P1P3 as the X-axis;

3: Set the direction perpendicular to P1P3 and P0 as the positive direction of the Y-axis;

4: Set the midpoint P4 of P1P3 as the origin (x0, y0);

5: Take $‖P_1{P}_3‖$ as the unit length of axis;

6: Construct the local coordinate system;

7: Set the center coordinate P5 of the ROI to $\left(x_0,y_0+\frac{5}{6}‖P_1{P}_3‖\right)$;

8: Set the side length of ROI to $‖P_1{P}_3‖$;

9: return segmented ROI