Question

In neighborhood operation for spatial filtering using square mask of n*n, which of the following approach is/are used to obtain a perfectly filtered result irrespective of the size?

(a) By padding the image

(b) By filtering all the pixels only with the mask section that is fully contained in the image

(c) By ensuring that center of mask must be at a distance ≥ (n – 1)/2 pixels from border of image

(d) None of the mentioned

I had been asked this question in exam.

I'm obligated to ask this question of Spatial Filtering in division Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

Right choice is (c) By ensuring that center of mask must be at a distance ≥ (n – 1)/2 pixels from border of image

Easiest explanation: By ensuring that center of mask must be at a distance ≥ (n – 1)/2 pixels from border of image, the resultant image would be of smaller size but all the pixels would be the result of the filter processing and so is a fully filtered result.

In the other approach like padding affect the values near the edges that gets more prevalent with mask size increase, while the another approach results in the band of pixels near border that gets processed with partial filter mask. So, not a fully filtered case.