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Median Filter

Purpose

This filter is used when you want to reduce random pixelized noise, i.e. noise that does not have a specific multipixel pattern.

Brief explanation of the algorithm

Taking a 3x3 pixel matrix, the algorithm calculates the statistical median of the values.
Example:
10 20 40
20 35 30
23 33 44

The median of those value is 30, so the value 30 is substituted to the one of the central pixel. The output matrix is:

10 20 40
20 30 30
23 33 44

Minimum Filter

Purpose

This filter has a similar behaviour with respect to the Median Filter, but producing a somewhat darker output. It is useful when you know that random pixel noise is made of brighter pixels than the surroundings.

Brief explanation of the algorithm

Taking a 3x3 pixel matrix, the algorithm calculates the statistical minimum of the values.
Example:
10 20 40
20 35 30
23 33 44

The minimum of those value is 10, so the value 10 is substituted to the one of the central pixel. The output matrix is:

10 20 40
20 10 30
23 33 44

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