Quaternion-based Local Binary Patterns for illumination invariant face recognition

Face recognition under varying illumination conditions has benefited from the encapsulation of face features into a quaternion representation. In particular, a quaternion-based representation encoding four LBP descriptors (one-pixel to four-pixel radius) has delivered interesting recognition scores when using just one training image per subject. However, each coefficient of such a representation only encapsulates the eight sampling values required for computing a classic LBP code. In this paper, we propose a quaternion representation which encodes additional LBP codes at each radius. Consequently, a wider pixel descriptor is obtained because further sampling values are considered in the region surrounding the reference pixel. Illumination invariant face verification and identification experiments are conducted by using only one training face image. The representation proposed improves the recognition rates reported by the representation only encapsulating classic LBP codes.