Corresponding author.Kezong Tang was born in 1978. He received his M.S. degree in pattern recognition and inteligent systems from Jiangsu University of Science and Technology in 2007. Currently, he is a Ph.D. candidate at School of Computer Science and Technology, Nanjing University of Science and Technology. His research interests include image processing and artificial intelligence. E-mail: tangkezong@ 126.com Jingyu Yang was born in 1941. He received the B.S. degree in computer science from Nanjing University of Science and Technology (NUST). He is currently a professor and chairman in the Department of Computer Science at NUST. His current research interests are in the areas of pat- tern recognition and robot vision. Haiyan Chen was born in 1984. She received her M.S. degree in computer science from Nanjing Normal University in 2006. Currently, she is a Ph.D. candidate at School of Computer Science and Technology, Nanjing University of Science and Technology. Her research interests are in image processing and pattern recognize. Shang Gao was born in 1972. He is a professor of Jiangsu University of Science and Technology. He received his doctor degree from Nanjing University of Science and Technology in 2006. His research interests are mainly in image processing and artificial intelligence.