Parent Topic: Filter

Average Filter

The Average (mean) filter smooths image data, thus eliminating noise. This filter performs spatial filtering on each individual pixel in an image using the grey level values in a square or rectangular window surrounding each pixel.

For example:

  a1 a2 a3            
  a4 a5 a6             3x3 filter window
  a7 a8 a9

The average filter computes the sum of all pixels in the filter window and then divides the sum by the number of pixels in the filter window:

Filtered pixel = (a1 + a2 + a3 + a4 ... + a9) / 9

NOTE: In order to filter pixels located near the edges of the image, edge pixel values are replicated to give sufficient data.

Parent Topic: Filter
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