Describe the median pass filter. DIP

Median Filter: Median filter, as the name implies, replaces the center value of a mask with the median of all the values of the mask. Simply taking some grey-scale values of an image and taking a 3×3 mask. Now we have 9 values and the 5th value is the median. Thus, the center value of the mask will be replaced by the median. So, the implementation of this filter is as follows,


  1. First of all, a mask has to be taken of odd number such as 3×3, 5×5 etc. Here taking 3×3.
  2. Now we will arrange the values of the mask in ascending or descending order to find the median.
  3. Then the median will be used to replace the center value of the mask.




Places to use this filter:

  1. This filter provides excellent noise reduction with considerably less blurring effect than low pass filter.
  2. Median filters are particularly effective in the presence of impulse noise, also called salt-and-peeper noise.

Disadvantages :

  1. Less but it also causes blur effect.
  2. Loss of sharpness.
  3. It also tends to turn an image to an image consisting almost similar grey-scale levels everywhere.

Author: Tanmay Chakrabarty

Tanmay Chakrabarty is a former CSE student, currently working as a Senior Software Engineer with 5+ years of experience in the field of Web Application development in PHP+MySQL platform with strong skills in Javascript, JQuery, JQuery UI and CSS. He tries to write notes every week but fails due to heavy loads of duty.

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