Question

In contrast stretching, if r1=s1 and r2=s2 then which of the following is true?

(a) The transformation is not a linear function that produces no changes in gray levels

(b) The transformation is a linear function that produces no changes in gray levels

(c) The transformation is a linear function that produces changes in gray levels

(d) The transformation is not a linear function that produces changes in gray levels

This question was posed to me by my college professor while I was bunking the class.

The doubt is from Basic Intensity Transformation Functions topic in portion Intensity Transformations and Spatial Filtering of Digital Image Processing

Answer 1

Right answer is (b) The transformation is a linear function that produces no changes in gray levels

To elaborate: The locations of points (r1,s1) and (r2,s2) control the shape of the transformation function. If r1=s1 and r2=s2 then the transformation is a linear function that produces no changes in gray levels.