In this paper we propose a novel image descriptor built by computing the covariance of pixel level features on densely sampled patches and encoding them using their covariance. Appropriate projections to the Euclidean space and feature normalizations are employed in order to provide a strong descriptor usable with linear classifiers. In order to remove border effects, we further enhance the Spatial Pyramid representation with bilinear interpolation. Experimental results conducted on two common datasets for object and texture classification show that the performance of our method is comparable with state of the art techniques, but removing any dataset specific dependency in the feature encoding step.
Covariance of Covariance Features for Image Classification / Serra, Giuseppe; Grana, Costantino; Manfredi, Marco; Cucchiara, Rita. - ELETTRONICO. - (2014), pp. 411-414. (Intervento presentato al convegno ACM International Conference on Multimedia Retrieval tenutosi a Glasgow nel Apr 1-4) [10.1145/2578726.2578781].