Object Classification Using Heterogeneous Co-occurrence Features

Co-occurrence features are effective for object classification because observing co-occurrence of two events is far more informative than observing occurrence of each event separately. For example, a color co-occurrence histogram captures co-occurrence of pairs of colors at a given distance while a color histogram just expresses frequency of each color. As one of such co-occurrence features, CoHOG (co-occurrence histograms of oriented gradients) has been proposed and a method using CoHOG with a linear classifier has shown a comparable performance with state-of-the-art pedestrian detection methods. According to recent studies, it has been suggested that combining heterogeneous features such as texture, shape, and color is useful for object classification. Therefore, we introduce three heterogeneous features based on co-occurrence called color-CoHOG, CoHED, and CoHD, respectively. Each heterogeneous features are evaluated on the INRIA person dataset and the Oxford 17/102 category flower datasets. The experimental results show that color-CoHOG is effective for the INRIA person dataset and CoHED is effective for the Oxford flower datasets. By combining above heterogeneous features, the proposed method achieves comparable classification performance to state-of-the-art methods on the above datasets. The results suggest that the proposed method using heterogeneous features can be used as an off-the-shelf method for various object classification tasks.