Question

If in an image there exist similar change in gray-level values in the image, which of the following shows a stronger response using second order derivative operator for sharpening?

(a) A line

(b) A step

(c) A point

(d) None of the mentioned

I have been asked this question in an international level competition.

My question is taken from Sharpening Spatial Filters-2 in section Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

Right option is (c) A point

For explanation: second order derivative shows a stronger response to a line than a step and to a point than a line, if there is similar changes in gray-level values in an image.