Figure 3

With edge pixels indexed, edge distances are calculated. In (a)-i to iii, the selected PS is at the center of the white box, which shows the edge detection boundary, and the raw edge pixels are indexed according to their distances to the PS. In (b)-i, the edges at different time frames are truncated to equal length to calculate edge distance. In (b)-ii to -iii, the calculation of distance for t = 1 and t = 9 is shown.