1. College of Electronic and Information Engineering, Machine Vision Engineering Research Center of Hebei Province, Hebei University, Baoding, China
2. College of Electronic and Information Engineering, Key Laboratory of Digital Medical Engineering of Hebei Province, Hebei University, Baoding, China
3. National Laboratory of Pattern Recognition, Institute of Automation, Chinese Academy of Sciences, Beijing, China
4. School of Computing and Mathematics, University of Leicester, Leicester, U.K.