A hybrid feature descriptor with Jaya optimised least squares SVM for facial expression recognition

Facial expression recognition has been a long-standing problem in the field of computer vision. This paper proposes a new simple scheme for effective recognition of facial expressions based on a hybrid feature descriptor and an improved classifier. Inspired by the success of stationary wavelet transform in many computer vision tasks, stationary wavelet transform is first employed on the pre-processed face image. The pyramid of histograms of orientation gradient features is then computed from the low-frequency stationary wavelet transform coefficients to capture more prominent details from facial images. The key idea of this hybrid feature descriptor is to exploit both spatial and frequency domain features which at the same time are robust against illumination and noise. The relevant features are subsequently determined using linear discriminant analysis. A new least squares support vector machine parameter tuning strategy is proposed using a contemporary optimisation technique called Jaya optimisation for classification of facial expressions. Experimental evaluations are performed on Japanese female facial expression and the Extended Cohn-Kanade (CK+) datasets, and the results based on 5-fold stratified cross-validation test confirm the superiority of the proposed method over state-of-the-art approaches.