grabcut: http://www.cnblogs.com/tornadomeet/archive/2012/11/09/2763271.html#top
http://blog.csdn.net/zouxy09/article/details/8535087
http://www.doc88.com/p-9009005080453.html
paper
原文：http://www.cnblogs.com/lucky-star-star/p/5059895.html
