Anat Levin Dani Lischinski Yair Weiss A Closed-Form Solution to Natural Image Matting. 228-242 2008 30 IEEE Trans. Pattern Anal. Mach. Intell. 2 http://doi.ieeecomputersociety.org/10.1109/TPAMI.2007.1177 db/journals/pami/pami30.html#LevinLW08