Regularized active shape model for shape alignment

Active shape model (ASM) statistically represents a shape by a set of well-defined landmark points and models object variations using principal component analysis (PCA). However, the extracted shape contour modeled by PCA is still unsmooth when the shape has a large variation compared with the mean shape. In this paper, we propose a regularized ASM (R-ASM) model for shape alignment. During training stage, we present a regularized shape subspace on which image smoothness constraint is imposed, such that the learned components to model shape variations should not only minimize reconstruction error but also obey smoothness principle. During searching stage, a coarse-to-fine parameter adjustment strategy is performed under Bayesian inference. It makes a desired shape smoother and more robust to local noise. Lastly, an inner shape is introduced to further regularize search results. Experiments on face alignment demonstrate the efficiency and effectiveness of our proposed approach.