Question

The transformation s = T(r) producing a gray level s for each pixel value r of input image. Then, if the T(r) is monotonically increasing in interval 0 ≤ r ≤ 1, what does it signifies?

(a) It guarantees the existence of inverse transformation

(b) It is needed to restrict producing of some inverted gray levels in output

(c) It guarantees that the output gray level and the input gray level will be in same range

(d) All of the mentioned

I had been asked this question in an interview.

The doubt is from Histogram Equalization and Processing topic in division Image Enhancement of Digital Image Processing

Answer 1

Correct option is (b) It is needed to restrict producing of some inverted gray levels in output

For explanation I would say: A T(r) which is not monotonically increasing, could result in an output containing at least a section of inverted intensity range. The T(r) is monotonically increasing in interval 0 ≤ r ≤ 1, is needed to restrict producing of some inverted gray levels in output.