Question

What condition prevents the intensity artifacts to be created while processing with contrast stretching, if r and s are gray-values of image before and after processing respectively?

(a) r1 = s1 and r2 = s2

(b) r1 = r2, s1 = 0 and s2 = L – 1, L is the max gray value allowed

(c) r1 = 1 and r2 = 0

(d) r1 ≤ r2 and s1 ≤ s2

I have been asked this question by my college professor while I was bunking the class.

My doubt stems from Piecewise-Linear Transformation Functions in section Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

The correct choice is (d) r1 ≤ r2 and s1 ≤ s2

To elaborate: While processing through contrast stretching, if r1 ≤ r2 and s1 ≤ s2 is maintained, the function remains single valued and so monotonically increasing. This helps in the prevention of creation of intensity artifacts.