SHEN Lin-Lin: Associate professor at the School of Computer and Software Engineering, Shenzhen University. He received his Ph.D. degree from University of Not-tingham, UK in 2005. Before joining Shen- zhen University, he had been working as a research fellow on MRI brain image pro- cessing at Medical School, University of Nottingham. His research interest covers image processing, pattern recognition, and biometrics. Corresponding author of this paper. E-mail: llshen@szu.edu.cn JI Zhen: Professor at Texas Instruments DSPs Laboratory, Shenzhen University. He received his bachelor and Ph.D. degrees from Xi'an Jiaotong University, in 1994 and 1999, respectively. In 2001, 2003, 2004, 2006, and 2007, he worked as an academic visitor in the Department of Electronics and Electrical Engineering, University of Liverpool, UK. His research interest covers DSP design, image coding, embedded system, computation intelligence, digital watermarking, and medical image processing. E-mail: jizhen@szu.edu.cn