Noncontact Palm Vein ROI Extraction Based on Improved Lightweight HRnet in Complex Backgrounds

Algorithm 1. ROI Extraction

1. Obtain three keypoints P1, P2, and P4;

2. Set the line through P2P4 as the X-axis;

3. Set the direction perpendicular to P2P4 and P1 as the positive direction of the Y-axis;

4. Set the midpoint Q of P2P4 as the origin ();

5. Take |P2P4| as the unit length of axis;

6. Construct the local coordinate system;

7. Obtain coordinate A of the ROI as (|P2P4|,|P2P4|),

  Obtain coordinate A of the ROI as (|P2P4|,|P2P4|),

  Obtain coordinate A of the ROI as (|P2P4|,|P2P4|),

  Obtain coordinate A of the ROI as (|P2P4|,|P2P4|),

8. Connect ABCD in turn to get ROI.

Algorithm 1. ROI Extraction