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Image compression using adaptive sparse representations over trained dictionaries

Sparse representation is a common approach for reducing the spatial redundancy by modelling an image as a linear combination of few atoms taken from an analytic or trained dictionary. This paper introduces a new image codec based on adaptive sparse representations wherein the visual salient information is considered into the rate allocation process. Firstly, the regions of the image that are more conspicuous to the human visual system are extracted using a classical graph-based method. Further, block-based sparse representation over a trained dictionary coupled with an adaptive sparse representation is proposed, such that the adaptivity is achieved by appropriately assigning more atoms of the dictionary to the blocks belonging to the salient regions. Experimental results show that the proposed method outperforms the existing image coding standards, such as JPEG and JPEG2000, which use an analytic dictionary, as well as the state-of-the-art codecs based on trained dictionaries.