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. 2016 Mar 29;11(3):e0152307. doi: 10.1371/journal.pone.0152307

Fig 3. Image-processing procedure for detecting the center of the pupil ellipse and the center of gravity of an iris freckle in mouse A.

Fig 3

(A) Original image of the left eye of mouse A. (B) Same eye as in (A) but in a contrast-enhanced image. (C) White areas are where the gray scale was less than the threshold value. Black rectangle shows the region of interest (ROI) for detecting the left edge of the pupil. (D) Left edge of the pupil was detected. (E) White areas are where the gray scale was less than the threshold value. Black rectangle shows the ROI for detecting the right edge of the pupil. (F) Right edge of the pupil was detected. (G) The edge of the pupil was approximated by the pupil ellipse and calculated at the center of the ellipse. (H) ROI for detecting an iris freckle was determined after calculating the pupil ellipse. The region was some distance from the center of the ellipse and had the same curvature as the ellipse. (I) In the region shown in (H), an iris freckle was detected with the gray scale less than the threshold value. (J) Coordinates of the iris freckle were calculated as the center of gravity of the white areas shown in (I).