For an image with intensity values r in the range [0, L − 1], which…
2021
For an image with intensity values r in the range [0, L − 1], which transformation produces the negative output intensity s?
Answer: A. s = L − 1 − r — CONCEPT A gray-level negative reverses the ordering of intensities while keeping every output inside the same range [0, L − 1]. For any input r, the distance…
- A.
s = L − 1 − r
- B.
s = L + r
- C.
s = L − r
- D.
s = L + 1 + r
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Correct answer: A
CONCEPT
A gray-level negative reverses the ordering of intensities while keeping every output inside the same range [0, L − 1]. For any input r, the distance of r from the upper endpoint becomes the output intensity.
APPLICATION
The highest allowed intensity is L − 1, so measure the complement of r from that endpoint.
Therefore s = (L − 1) − r.
At r = 0, the output is s = L − 1; at r = L − 1, the output is s = 0. Intermediate intensities reverse in the same way.
CROSS-CHECK
Applying the transformation twice gives (L − 1) − [(L − 1) − r] = r, so the original intensity is recovered. Hence the negative transformation is s = L − 1 − r.