A hybrid rotation-invariant face recognition system using Log-Polar Transform

The recognition of human faces, especially those with different orientations is a challenging and important problem in image analysis and classification. This paper proposes an effective schema for rotation invariant face recognition using log-polar transform and discrete cosine transform combined features. The rotation invariant feature extraction for a given face image involves applying the log-polar transform to eliminate the rotation effect and to produce a row shifted log-polar image. The discrete cosine transform is then applied to eliminate the row shift effect and to generate the low-dimensional feature vector. A particle swarm optimization based feature selection algorithm is utilized to search the feature vector space for the optimal feature subset. Evolution is driven by a fitness function defined in terms of maximizing the between-class separation (scatter index). Experimental results based on the ORL face database using testing data sets for face images with different orientations show that the proposed system outperforms other face recognition methods. The overall recognition rate for the rotated test images being 97%, demonstrating that the extracted feature vector is an effective rotation invariant feature set with minimal set of selected features.