Design technique for two-directional recursive filters

This work approaches the design of a class of 2D recursive filters, with a two-directional orientation-selective frequency response. We propose two design methods based on a given 1D digital prototype filter and frequency transformations, one completely analytical, including the bilinear transform, and another which uses a numerical approximation stage. These filters may find useful applications in image processing, like detecting lines with a given orientation from an image, as we show through simulation results. The resulted filters are very efficient, being at the same time of low complexity and relatively high selectivity. Simulation results are provided which show their image filtering capabilities.