Adaptive Multi-Shell Mdian Filter for Improving Image Quality
Narupon Panakulchaiwit, Danai Lisaw Atdiratanakul, Kobachai Dejhan and Fusak Cheevasuvit
Faculty of Engineering,
King Mongkut's Institute of Technology Ladkrabang, Ladkrabang,
Bangkok 10520, Thailand
Tel : 66-2-3269967, 66-2-3269081, Fax : 66-2-3269086
Email :kobachai@telelan.telecom.eng.kmitl.ac.th
Chatcharin Soonyeekan
Faculty of Engineering,
Kasem Bundit University, Pattankaran Road,
Bangkok 10520, Thailand
Abstract
To display the images is difficult, the main problem is the impulse noise (or salt and pepper noise). This paper proposes two algorithms to improve the impulse noise for obtaining the better image quality than the regular method (or fixed length) median filters when the images are corrupted by impulse noise. The advantages of this algorithm is easy to implement, when realized for hardware implementation and the additional circuits are rather simple. Furthermore, the algorithms can easily be integrated into efficient hardware realizations for median filers. The performance of proposed filters can be compared with regular median filters (fixed length or standard median filters for window size 3x3).
Introduction
The two-dimensional median can eliminate the impulse noise without the loss of edge information [1],but it is difficult to maintain the picture details, especially the small window such as 3x3. This condition is really for any amount of impulse noise, thus it is a disadvantage of 3x3 windows. This paper investigates to use 5 x 5 windows and it reduced the effect of discrete impulse noise on an image. The disadvantage results in blurred edged are increased for the higher window. Many techniques have previously proposed [2-5].
This paper investigates two algorithm of two-dimensional median filter. The first is 3x3 multi-shell constant window, it is good for image noise smoothing and sharp step edges is small amount of impulse noise. The second is the automatically adjustable window size. It improves any problem of constant window and give the low blurred edges with high sharp. It can be used for the case of any amount of impulse noise.
Theory
The salt and pepper noise has gray level with higher low that is different from the neighborhood point with a short time. It is obviously to see, thus the disturbance model can be carried out as follows;
S
ij = gray level of original image at point (i,j)
X
ij = gray level of disturbanced image at point (i,j)
n = noise signal level
X
ij = Sij for the probability is (1-p)
X
ij = Sij + n for the probability is p
P = probability of disturbance
n has uniform disturbution; 0<n<(255-S
ij) for salt noise and -S
ij<n<0 for pepper noise.
The experimental image has the gray level between 0 to 255. Therefore, the salt noise ha the maximum not more tan 255, for the pepper noise has the minimum value equal to 0. In the experiment will use both of the noises for the same time.
