Noise

Noise means an unwanted signal. Image/video noise means unwanted variations in intensity (for grayscale image) or colors (for color images) that are not present in the real object being photographed or recorded. Image noise is a form of electronic disruption and could come from many sources, such as camera sensors and circuitry in digital or analog cameras. Noise in digital cameras is equivalent to the film grain of analog cameras. Though some noise is always present in any output of electronic devices, a high amount of image noise considerably degrades the overall image quality, making it useless for the intended purpose. To represent the quality of the electronic output (in our case, digital images), the mathematical term signal-to-noise ratio (SNR) is a very useful term. Mathematically, it's defined as follows:

Note

More signal-to-noise ratio translates into better quality image.

Kernels for noise removal

In the following concepts and their implementations, we are going to use kernels...