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In this paper, a novel decision-based filter, called the multiple thresholds switching (MTS) filter, is proposed to restore images corrupted by salt-pepper impulse noise. The filter is based on a detection-estimation strategy. The impulse detection algorithm is used before the filtering process, and therefore only the noise-corrupted pixels are replaced with the estimated central noise-free ordered mean value in the current filter window. The new impulse detector, which uses multiple thresholds with multiple neighborhood information of the signal in the filter window, is very precise, while avoiding an undue increase in computational complexity. For impulse noise suppression without smearing fine details and edges in the image, extensive experimental results demonstrate that our scheme performs significantly better than many existing, well-accepted decision-based methods.

Keywords: image restoration, filter, threshold, impulse detector, impulse noise

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Received December 17, 2003; revised June 1 & October 11, 2004; accepted November 15, 2004.
Communicated by Pau-Choo Chung.
^* This work is supported by National Science Council of the Republic of China under Grant NSC922213E194020.