Learning statistically relevant edge structure improves low-level visual descriptors

Over the recent years, low-level visual descriptors, among which the most popular is the histogram of oriented gradients (HOG), have shown excellent performance in object detection and categorization. We form a hypothesis that the low-level image descriptors can be improved by learning the statistically relevant edge structures from natural images. We validate this hypothesis by introducing a new descriptor called the histogram of compositions (HoC). HoC exploits a learnt vocabulary of parts from a state-of-the-art hierarchical compositional model. Furthermore, we show that HoC is a complementary descriptor to HOG. We experimentally compare our descriptor to the popular HOG descriptor on the task of object categorization. We have observed approximately 4% improved categorization performance of HoC over HOG at lower dimensionality of the descriptor. Furthermore, in comparison to HOG, we show a categorization improvement of approximately 11% when combining HOG with the proposed HoC.