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. Author manuscript; available in PMC: 2016 May 1.
Published in final edited form as: IEEE J Biomed Health Inform. 2014 Jun 30;19(3):1153–1167. doi: 10.1109/JBHI.2014.2329493

Fig. 3.

Fig. 3

(a) Original image. O represents a reference point. Red dash arrow represents direction unit. Blue solid arrow denotes image gradient. Five typical points are represented by A1–A5. (b) Conventional image edges. (c) Directional image edges.