Figure 2.

Processing steps to extract the pupil center point. (A) the original grayscale image; (B) the black and white thresholded image; (C) the segmented image in which each segment is displayed in a different color; (D) a highlighted segment (red) with its border extracted using Convex Hull method (green border), which actually covers some part of the pupil; The angle of each point on the border is calculated using the yellow lines and the horizontal white line that meet at the center of the segment (E) the decomposition of the shown border into its sinusoidal components with each point being an edge on the green border shown in (D); and (F) the extracted pupil (blue ellipse) and the estimated pupil center point (cyan cross).