Removal of Blotches and Impulse Noise in Gray Scale Images Using Non-linear Algorithm

Abstract

An image consists of artifact, which appears in an image that is actually not present in the original imaged object. An image artifact (noise) is sometimes the result of improper operation of the imager, and other times a consequence of natural processes or properties of the human body. Blotches (bulk noise) and impulses are the artifacts where blotch can be either bright or dark spots and impulse can be salt and pepper noise or random-valued noise. The proposed algorithm is implemented in two steps. In the first step, based on the certain threshold value all the pixels in image are identified as corrupted/uncorrupted pixels. In the second step, the new pixel value is estimated only for the corrupted pixels. The algorithm uses an adaptive length window whose maximum size is 5 × 5 to avoid blurring due to large window sizes. However, the restricted window size renders median operation less effective whenever noise is excessive in which case the proposed algorithm automatically switches to mean filtering.