Fig. 3From: Characterization of the retinal vasculature in fundus photos using the PanOptic iExaminer systemExample of retinal vessel density analysis. a Cropped square photograph. b Grayscale conversion using Gray = MAX Contrast. c Contrast enhancement using contrast limited adaptive histogram equalization. d Vessel border enhancement using the linear filter and edge enhancement. e Vessel extraction using U-Net. f Vessel binary conversion using ImageJBack to article page