The key to image restoration is to establish a degradation model. The original image f(x, y) is degraded to image g(x, y) through system h and additive noise n(x, y), as shown in the following figure.

f(x，y)

n(x，y)

H

The mathematical expression of the degradation process of this image can be written as:

g(x，y)=H[f(x，y)]+n(x，y)

Textbook 103 has pictures.