Removal of impulse noise from highly corrupted images by using noise position information and directional information of image

Abstract

AbstractOne excellent method for restoration of images with superposed impulsive noise uses the position information of the impulsive noise for the pixels used for processing and of the processing point. This method consists of two steps. In Step 1, the impulsive noise existing in the image is detected and the noise position image is formed. In Step 2, by using the noise position image formed in Step 1, the filter processing is carried out on the pixels degraded by impulsive noise only with the pixels not affected by the impulsive noise. An excellent procedure for Step 2, using an average filter (PSA filter), has been proposed. However, in the method with an average filter, a uniform weight is provided on all pixels in the filter window. Therefore, if the generation probability of the impulsive noise is increased, the window size cannot be increased even if the filter window size should be increased. Also, an individual image has directionality specific to the image. This directionality is not taken into account in the filter processing. In the present paper, in order to resolve this problem, a PSWA filter is proposed for the filter processing in Step 2 by using the weighted average filter with weights considering the distance from the process point and the directionality of the image. In order to appropriately apply the proposed filter, there are two parameters (window size N and parameter κ) to be set. From experimental investigation, it is found that these two parameters do not depend on the type of the original image but only on the generation probability of the impulsive noise. Further, from the generation probability of the impulsive noise, the method for providing these two parameters is presented specifically. The effectiveness of the proposed method is confirmed through several processing examples. © 2002 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 86(3): 33–43, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.1138