Histogram of oriented gradients (HOG) descriptor was initially applied to human detection and achieved great success. In recent years, HOG descriptor has also been applied to face recognition. However, comparing with other sophisticated feature descriptors such as LBP, Gabor and so on, there are still considerable research space on the application of HOG features for face recognition. There are two main contributions. On one hand, the main parameters are statistically analysed characterising HOG descriptor for face recognition, which seems to be not discussed clearly in literatures so far. On the other hand, a novel framework for face recognition based on the fusion of global and local HOG features has been proposed. Face images are first illumination normalised by the DoG filter. Secondly, global and local HOG features are extracted by PCA + LDA or LDA with different framework. Finally, in decision level, global and local classifiers are built by the nearest neighbour classifier, after that, two classifiers are fused by a weighted sum rule. Experimental results on two large‐scale face databases FERET and CAS‐PEAL‐R1 show that, in comparison with 12 state‐of‐the‐art approaches of face recognition, the proposed method achieves the highest average recognition rate.

Dimensionality reduction is vital in many fields, and alignment-based methods for nonlinear dimensionality reduction have become popular recently because they can map the high-dimensional data into a low-dimensional subspace with the property of local isometry. However, the relationships between patches in original high-dimensional space cannot be ensured to be fully preserved during the alignment process. In this paper, we propose a novel method for nonlinear dimensionality reduction called local coordinates alignment with global preservation. We first introduce a reasonable definition of topology-preserving landmarks (TPLs), which not only contribute to preserving the global structure of datasets and constructing a collection of overlapping linear patches, but they also ensure that the right landmark is allocated to the new test point. Then, an existing method for dimensionality reduction that has good performance in preserving the global structure is used to derive the low-dimensional coordinates of TPLs. Local coordinates of each patch are derived using tangent space of the manifold at the corresponding landmark, and then these local coordinates are aligned into a global coordinate space with the set of landmarks in low-dimensional space as reference points. The proposed alignment method, called landmarks-based alignment, can produce a closed-form solution without any constraints, while most previous alignment-based methods impose the unit covariance constraint, which will result in the deficiency of global metrics and undesired rescaling of the manifold. Experiments on both synthetic and real-world datasets demonstrate the effectiveness of the proposed algorithm.