Performance comparisons of sparse coefficients from BDL model and from WBDL model. We selected 200 images from 10 random persons in AR database [18
] for training and the remaining 60 images for testing. Proto dictionary contains 10 blocks; each block contains 5 atoms. The sparse coefficients of 60 testing samples in BDL model are shown in (a) and the weighted sparse coefficients of the same 60 testing samples in WBDL model are shown in (b).