
Chapter 5
Denoising
5.1 Introduction
Noise is always present in images, regardless of the way they have been
acquired. Movies shot in film have an intrinsic film grain, digital movies have
noise due to the acquisition process (Chapter 3) and the subsequent compres-
sion (Chapter 4) and transmission. Denoising is therefore a very important
problem in image processing, with a vast literature on it and with early works
dating back to the 1960s.
Classic denoising techniques were mostly based in one of these two ap-
proaches: modification of transform coefficients (using the Fourier transform,
the DCT, some form of wavelet, etc.), or averaging image values (in