Design method for a class of maximally-flat spatial linear filters

This paper presents a design method for a specific class of spatial linear filters, namely maximally-flat 2-D IIR zero-phase filters. The design is achieved in the frequency domain and relies directly on the currently-used temporal filters using the well-known maximally-flat approximation. The proposed design method is more general and works for several types of filters, as long as the transfer function of the prototype filter is available. However, as a particular sub-class, we chose to design maximally-flat filters of two types, namely circularly-symmetric and orientation-selective. Although the designed filters are implemented in the CNN framework, they can be as well regarded as discrete spatial filters, which can be implemented digitally using the currently available techniques.