Question

Which of the following are forced to the median intensity of the neighbors by n*n median filter?

(a) Isolated cluster of pixels that are light or dark in comparison to their neighbors

(b) Isolated cluster of pixels whose area is less than one-half the filter area

(c) All of the mentioned

(d) None of the mentioned

This question was posed to me during a job interview.

The above asked question is from Smoothing Nonlinear Spatial Filter in chapter Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

Right choice is (c) All of the mentioned

The explanation: The isolated cluster pixel value doesn’t come as a median value and since are either are light or dark as compared to neighbors, so are forced with median intensity of neighbors that aren’t even close to their original value and so are sometimes termed “eliminated”.

If the area of such isolated pixels are < n2/2, that is again the pixel value won’t be a median value and so are eliminated.

Larger cluster pixels value are more pronounced to be a median value, so are considerably less forced to median intensity.