Image coding using redundant dictionaries

This chapter discusses the problem of coding images using very redundant libraries of waveforms, also referred to as dictionaries. We start with a discussion of the shortcomings of classical approaches based on orthonormal bases. More specifically, we show why these redundant dictionaries provide an interesting alternative for image representation. We then introduce a special dictionary of 2-D primitives called anisotropic refinement atoms that are well suited for representing edge-dominated images. Using a simple greedy algorithm, we design an image coder that performs very well at low bit rate. We finally discuss its performance and particular features such as geometric adaptativity and rate scalability.