IMPULSE NOISE REMOVAL USING POLYNOMIAL-APPROXIMATION

A novel filtering algorithm is presented to restore images corrupted b y impulsive noise. As a preprocessing procedure of the noise cancellat ion 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 wh en it is considered as an impulse; otherwise, it is left unchanged, an d (2) only the values of the good pixels are employed as useful inform ation by the noise cancellation filter. To remove noises from the corr upted image, we propose a new filter called a polynomial approximation (PA) filter, which is developed by modeling a local region with a pol ynomial that can best approximate the region under the condition of le ast squared error. Furthermore, an adaptive approach is introduced to automatically determine the orders of the polynomials. The proposed tw o kinds of PA filters, fixed-order and adaptive-order PA filters, are tested on images corrupted by both fixed-valued and random-valued impu lsive noise. Major improvements are obtained in comparison with other state-of-the-art algorithms. (C) 1998 Society of Photo-Optical Instrum entation Engineers.