Thermal face recognition in unconstrained environments using histograms of LBP features

Several studies have shown that the use of thermal images can solve limitations of visible spectrum based face recognition methods operating in unconstrained environments. The recognition of faces in the thermal domain can be tackled using the histograms of Local Binary Pattern (LBP) features method. The aim of this work is to analyze the advantages and limitations of this method by means of a comparative study against other methods. The analyzed methods were selected by considering their performance in former comparative studies, in addition to being real-time - 10 fps or more - to require just one image per person, and to being fully online (no requirements of offline enrollment). Thus, in the analysis the following local-matching based methods are considered: Gabor Jet Descriptors (GJD), Weber Linear Discriminant (WLD) and Local Binary Pattern (LBP). The methods are compared using the UCHThermalFace database. The use of this database allows evaluating the methods in real-world conditions that include natural variations in illumination, indoor/outdoor setup, facial expression, pose, accessories, occlusions, and background. In addition, the fusion of some variants of the methods was evaluated. The main conclusions of the comparative study are: (i) All analyzed methods perform very well under the conditions in which they were evaluated, except for the case of GJD that has low performance in outdoor setups; (ii) the best tradeoff between high recognition rate and fast processing speed is obtained by LBP-based methods; and (iii) fusing some methods or their variants improve the results up to 5 %.