Impulse Noise Removal Algorithms for IAP

Abstract

In this chapter, a novel filtering algorithm is presented to restore images corrupted by impulsive noise. As a pre-processing procedure of the noise cancellation filter, an improved impulse detector is used to generate a binary flag image which gives each pixel a flag indicating whether it is an impulse. This flag image has two uses: 1) A pixel is modified only when it is considered as an impulse; otherwise, it is left unchanged. 2) Only the values of the good pixels are employed as useful information by the noise cancellation filter. Section 7.2 describes the impulse noise model assumed by our experiments and presents an iterative impulse detection algorithm which provides us with more accurate detecting results than those of previously proposed methods. To remove noises from the corrupted image, in Section 7.3, we propose a new filter called polynomial approximation (PA) filter which is developed by modeling a local region with a polynomial that can best approximate the region under the condition of least square error. Section 7.4 introduces an adaptive approach that can automatically determine the orders of the polynomials. The proposed two kinds of PA filters, fixed-order and adaptive-order PA filters, are tested on images corrupted by both fixed-valued and random-valued impulsive noise. Some further simulation and comparison results are given in Section 7.5. Finally, a brief conclusion is drawn in Section 7.6.