1. Shen Zhen Polytechnic, Shenzhen, Guangdong Province 518055, P. R. China
2. State Key Laboratory of Pulp and Paper Engineering, South China University of Technology, Guangzhou, Guangdong Province 510640, P. R. China
3. School of Remote Sensing and Information Engineering, Wuhan University, Hubei Province 430079, P. R. China