Noise in digital images typically arises during image acquisition and transmission. It affects image quality due to factors like sensor imperfections, low light, high temperature, and transmission interference (e.g., lightning in wireless transmission).
Noise Characteristics:
- Spatial Properties: Define how noise is spread across an image.
- Frequency Properties: Refers to noise characteristics in the frequency domain. For example, noise with a constant Fourier spectrum is called white noise.
- Assumption: Noise is mostly assumed to be independent of spatial coordinates and uncorrelated with the image.
Important Noise Models (Probability Density Functions – PDFs):
Each model defines how noise values (intensity levels) are distributed statistically in an image.
The mean of salt-and-pepper noise is given by
