# Image Processing - Noise and denoise

2019-03-20

Computer Vision

466

Types of Noise
Additive noise
Additive noise is independent from image signal. The image g with nosie can be considered as the sum of ideal image f and noise n.[1]
Multiplicative noise
Multifplicative noise is often dependent on image signal. The relation of image and noise is[1]:
Gaussian noise
Gaussian noise, named after Carl Friedrich Gauss, is statistical noise having a probability density function (PDF) equal to that of the normal distribution, aka. the Gaussian distribution. i.e. the values that the noise can take on are Gaussian-distributed.
The PDF of a Gaussian random variable is given by[2]:
Salt-and-pepper noise
Fat-tail distributed or "impulsive" noise is sometimes called salt-and-pepper nosie or spike noise. An image containing salt-and-pepper noise will have dark pixels in bright regions and bright pixels in dark regions.[2]
The PDF of (Bipolar) Impulse noise is given by:
if b > a, gray