Among the many factors contributing to image quality degradation, noise is one of the
most recurrent and difficult elements to deal with. Smart filters capable to remove noise without
affecting the tiny details of a digital image are of primary importance to produce pleasant pictures.
Different noise sources, having different characteristics, are superimposed to the image signal;
consequently, the design of effective filters capable to discriminate and remove unwanted signal
from useful data, requires analysis and understanding of the whole image formation process. This
Chapter is devoted to the analysis of the main noise sources that contaminate the ideal image
signal, providing an overview of noise estimation and filtering techniques.
