Directional difference‐based switching median filters

Abstract

In this paper, a new median filter is proposed that has robustness without relying on the noise generation probability. The proposed filter has a configuration with an impulse detector in the prior stage of the filter. Since this detector has a superior signal estimation capability of the directional difference filter, impulse noise can be detected effectively even if generated at a high generating ratio and as a burst. In the median filter in the later stage, inclusion of the output values of the directional filter and successive updating of the signal values (successive process) are introduced. Hence, while the noise elimination capability of the conventional median filter is retained, the signal preservation at the details and edges can be improved. Therefore, the noise elimination filter proposed in this paper is abundant in robustness against variations of the gray scale, the generation probability, and the impulse adding situation. Its restoration results for images with superposed impulse noise at a high generation probability confirm the improvement of performance. In this paper, the effectiveness of the proposed impulse detector is first demonstrated. It is proven through processing examples that a better image processing result can be obtained from its combination with a newly configured median filter. At the same time, the robustness of the proposed procedure under various conditions is demonstrated. The effectiveness of the proposed method in the final restored image is verified. © 2001 Scripta Technica, Electron Comm Jpn Pt 3, 85(3): 22–32, 2002