[Zhou, Guangyou;He, Tingting] Cent China Normal Univ, Sch Comp, Wuhan 430079, Hubei, Peoples R China.^[Zhao, Jun] CASIA, Natl Lab Pattern Recognit, Beijing 100190, Peoples R China.^[Wu, Wensheng] Univ Southern Calif, Comp Sci Dept, Los Angeles, CA 90089 USA.