Consider a noisy image g(x, y) formed by the addition of noise h(x, y) to an original image f(x, y); that is, g(x, y) = f(x, y) + h(x, y) where the assumption is that at every pair of coordinates (x, y) the noise is uncorrelated† and has zero average value. The objective of the … Read more
The inverse filtering approach has poor performance. The wiener filtering approach uses the degradation function and statistical characteristics of noise into the restoration process.The objective is to find an estimate of the uncorrupted image f such that the mean square error between them is minimized. The error measure is given by Where E{.} is the … Read more
The simplest approach to restoration is direct inverse filtering where we complete anestimate of the transform of the original image simply by dividing the transform of the degraded image G(u,v) by degradation function H(u,v) We know that Therefore From the above equation we observe that we cannot recover the undegraded image exactly because N(u,v) is … Read more
A notch filter rejects (or passes) frequencies in predefined neighborhoods about a center frequency. Due to the symmetry of the Fourier transform notch filters must appear in symmetric pairs about the origin. The transfer function of an ideal notch reject filter of radius D0 with centers a (u0,v0) and by symmetry at (-u0 , v0) … Read more
The function of a band pass filter is opposite to that of a band reject filter It allows a specific frequency band of the image to be passed and blocks the rest of frequencies. The transfer function of a band pass filter can be obtained from a corresponding band reject filter with transfer function Hbr(u,v) … Read more
Arithmetic Mean filter: It is the simplest mean filter. Let Sxy represents the set of coordinates in the sub image of size m*n centered at point (x,y). The arithmetic mean filter computes the average value of the corrupted image g(x,y) in the area defined by Sxy. The value of the restored image f at any … Read more
The principal source of noise in digital images arises during image acquisition and /or transmission. The performance of imaging sensors is affected by a variety of factors, such as environmental conditions during image acquisition and by the quality of the sensing elements themselves. Images are corrupted during transmission principally due to interference in the channels … Read more
Restoration improves image in some predefined sense. It is an objective process. Restoration attempts to reconstruct an image that has been degraded by using a priori knowledge of the degradation phenomenon. These techniques are oriented toward modeling the degradation and then applying the inverse process in order to recover the original image. Restoration techniques are … Read more