Edge extraction using zero-frequency resonator

This paper proposes an approach based on the zero-frequency resonator to extract the edge information of the images. The proposed approach is counterintuitive to the concept that edges correspond to high-frequency components of an image. The impulse-like characteristics of edges in an image distribute the energy uniformly over all frequencies of the spectrum including around the zero-frequency. This property is exploited in this paper by using the output of a zero-frequency resonator, for extracting the edge information. Spatial domain and Fourier domain methods are employed to realize the zero-frequency resonator for two-dimensional signals. The Laplacian of the Gaussian (LOG) and the proposed approach are similar in the sense that the former approach uses a Gaussian filter for smoothing operation, whereas a zero-frequency resonator is used in the proposed approach. The output of the resonator is processed using a Laplacian operator for the trend removal. In the resulting filtered image, the edge information is present at the zero-crossings, and the edges are extracted using sign correspondence principle to identify the zero-crossings corresponding to the edges. Results of edge extraction are illustrated for a few clear and noisy images.