Descriptive local feature groups for image classification

In the conventional bag of visual words (BoW) based image representation, single visual word is not discriminative enough and the spatial contextual information among local image features is ignored. In this paper, descriptive local feature groups are proposed to address these two problems. First, local image features are refined by slightly transforming the original image. Then they are clustered and represented by visual words. Second, the candidate local feature groups are generated by searching the neighbors of every local image features. This kind of grouping shows more discriminative power than a single feature and the local spatial contexts can be catched. Third, we obtain the groups more descriptive to the object category by defining a significance score and the groups with high score are selected. Finally, the high order descriptive local feature groups are integrated to the vector based object categorization framework by a feature reweighting strategy. Experimental results on Scene-15 and Caltech 101 demonstrate the superior performance of our method.