A Hierarchical Probabilistic Model for Rapid Object Categorization in Natural Scenes
Each structure is a structured patch compiled from images of natural objects and scenes. To obtain a set of natural object and context structures, we performed ICA on patches of natural scenes and classified the ICs into four orientations. We then sampled a large number of patches from natural scenes and classified each patch as being oriented in one of the four orientations according to the root total square amplitude of the ICs at that orientation. We applied this procedure to a collection of 3×3 small patches and its corresponding 1×1 big patch. A structure was thus a pair of 3×3 structured patches and its corresponding 1×1 structured patch. The structures shown here were the average of all patches that shared same dominant orientational structure at two spatial scales.