![Noise salt and pepper](https://upload.wikimedia.org/wikipedia/commons/f/f4/Noise_salt_and_pepper.png)
Salt-and-pepper noise, also known as impulse noise, is a form of
noise
Noise is unwanted sound considered unpleasant, loud or disruptive to hearing. From a physics standpoint, there is no distinction between noise and desired sound, as both are vibrations through a medium, such as air or water. The difference aris ...
sometimes seen on
digital images. This noise can be caused by sharp and sudden disturbances in the image signal. It presents itself as sparsely occurring white and black
pixel
In digital imaging, a pixel (abbreviated px), pel, or picture element is the smallest addressable element in a raster image, or the smallest point in an all points addressable display device.
In most digital display devices, pixels are the ...
s.
An effective
noise reduction method for this type of noise is a
median filter
The median filter is a non-linear digital filtering technique, often used to remove noise from an image or signal. Such noise reduction is a typical pre-processing step to improve the results of later processing (for example, edge detection on an ...
or a
morphological filter. For reducing either salt noise or pepper noise, but not both, a
contraharmonic mean In mathematics, a contraharmonic mean is a function complementary to the harmonic mean. The contraharmonic mean is a special case of the Lehmer mean, L_p, where ''p'' = 2.
Definition
The contraharmonic mean of a set of positive numbers is defin ...
filter can be effective.
See also
*
Defective pixel
A defective pixel is a pixel on a liquid crystal display (LCD) that is not functioning properly. The ISO standard ISO 13406-2 distinguishes between three different types of defective pixels, while hardware companies tend to have further distingu ...
References
Noise (graphics)
Digital photography
Image noise reduction techniques
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