Dirichlet-tree Distribution Enhanced Random Forests for Head Pose Estimation

Head pose estimation is important in human-machine interfaces. However, illumination variation, occlusion and low image resolution make the estimation task difficult. Hence, a Dirichlet-tree distribution enhanced Random Forests approach (D-RF) is proposed in this paper to estimate head pose efficiently and robustly under various conditions. First, PCA based sub-features space from Gabor features and histogram distributions of the facial patches are extracted to eliminate the influence of occlusion and noise. Then, the D-RF is proposed to estimate the head pose in a coarse-to-fine way. In order to improve the discrimination capability of the approach, an adaptive Gaussian mixture model is introduced in the tree distribution. The proposed method has been evaluated with different data sets spanning from -90° to 90° in vertical and horizontal directions under various conditions. The experimental results demonstrate the approach’s robustness and efficiency.