Question

What is the name of the filter that is used to turn the average value of a processed image zero?

(a) Unsharp mask filter

(b) Notch filter

(c) Zero-phase-shift-filter

(d) None of the mentioned

I got this question in an interview for job.

My doubt is from Filtering in Frequency Domain in chapter Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

The correct answer is (b) Notch filter

Best explanation: Notch filter sets F (0, 0), to zero, hence setting up the average value of image zero. The filter is named so, because it is a constant function with a notch at origin and so is able to set F (0, 0) to zero leaving out other values.