Fig. 1. (a) Chain code representation; (b) coordinate representation

Fig. 2. Border representation

Fig. 3. Repeated search area

Fig. 4. Boundary point location

Fig. 5. Gray as a redundant area

Fig. 6. Algorithm flow chart

Fig. 7. Boundary chain search for redundancy

Fig. 8. Original binary image

Fig. 9. Boundary tracking result of Ref.[8]

Fig. 10. Boundary tracking result of Ref.[9]

Fig. 11. Boundary tracking result of proposed algorithm

Fig. 12. Inner hole image. (a) Original image; (b) tracking results of Ref.[9]; (c) tracking results of proposed algorithm