This set of Digital Image Processing Multiple Choice Questions & Answers (MCQs) focuses on “Sharpening Spatial Filters”.

1. Which of the following is the primary objective of sharpening of an image?

a) Blurring the image

b) Highlight fine details in the image

c) Increase the brightness of the image

d) Decrease the brightness of the image

View Answer

Explanation: The sharpening of image helps in highlighting the fine details that are present in the image or to enhance the details that are blurred due to some reason like adding noise.

2. Image sharpening process is used in electronic printing.

a) True

b) False

View Answer

Explanation: The applications of image sharpening is present in various fields like electronic printing, autonomous guidance in military systems, medical imaging and industrial inspection.

3. In spatial domain, which of the following operation is done on the pixels in sharpening the image?

a) Integration

b) Average

c) Median

d) Differentiation

View Answer

Explanation: We know that, in blurring the image, we perform the average of pixels which can be considered as integration. As sharpening is the opposite process of blurring, logically we can tell that we perform differentiation on the pixels to sharpen the image.

4. Image differentiation enhances the edges, discontinuities and deemphasizes the pixels with slow varying gray levels.

a) True

b) False

View Answer

Explanation: Fundamentally, the strength of the response of the derivative operative is proportional to the degree of discontinuity in the image. So, we can state that image differentiation enhances the edges, discontinuities and deemphasizes the pixels with slow varying gray levels.

5. In which of the following cases, we wouldn’t worry about the behaviour of sharpening filter?

a) Flat segments

b) Step discontinuities

c) Ramp discontinuities

d) Slow varying gray values

View Answer

Explanation: We are interested in the behaviour of derivatives used in sharpening in the constant gray level areas i.e., flat segments, and at the onset and end of discontinuities, i.e., step and ramp discontinuities.

6. Which of the following is the valid response when we apply a first derivative?

a) Non-zero at flat segments

b) Zero at the onset of gray level step

c) Zero in flat segments

d) Zero along ramps

View Answer

Explanation: The derivations of digital functions are defined in terms of differences. The definition we use for first derivative should be zero in flat segments, nonzero at the onset of a gray level step or ramp and nonzero along the ramps.

7. Which of the following is not a valid response when we apply a second derivative?

a) Zero response at onset of gray level step

b) Nonzero response at onset of gray level step

c) Zero response at flat segments

d) Nonzero response along the ramps

View Answer

Explanation: The derivations of digital functions are defined in terms of differences. The definition we use for second derivative should be zero in flat segments, zero at the onset of a gray level step or ramp and nonzero along the ramps.

8. If f(x,y) is an image function of two variables, then the first order derivative of a one dimensional function, f(x) is:

a) f(x+1)-f(x)

b) f(x)-f(x+1)

c) f(x-1)-f(x+1)

d) f(x)+f(x-1)

View Answer

Explanation: The first order derivative of a single dimensional function f(x) is the difference between f(x) and f(x+1).

That is, ∂f/∂x=f(x+1)-f(x).

9. Isolated point is also called as noise point.

a) True

b) False

View Answer

Explanation: The point which has very high or very low gray level value compared to its neighbours, then that point is called as isolated point or noise point. The noise point of is of one pixel size.

10. What is the thickness of the edges produced by first order derivatives when compared to that of second order derivatives?

a) Finer

b) Equal

c) Thicker

d) Independent

View Answer

Explanation: We know that, the first order derivative is nonzero along the entire ramp while the second order is zero along the ramp. So, we can conclude that the first order derivatives produce thicker edges and the second order derivatives produce much finer edges.

11. First order derivative can enhance the fine detail in the image compared to that of second order derivative.

a) True

b) False

View Answer

Explanation: The response at and around the noise point is much stronger for the second order derivative than for the first order derivative. So, we can state that the second order derivative is better to enhance the fine details in the image including noise when compared to that of first order derivative.

12. Which of the following derivatives produce a double response at step changes in gray level?

a) First order derivative

b) Third order derivative

c) Second order derivative

d) First and second order derivatives

View Answer

Explanation: Second order derivatives produce a double line response for the step changes in the gray level. We also note of second-order derivatives that, for similar changes in gray-level values in an image, their response is stronger to a line than to a step, and to a point than to a line.

**Sanfoundry Global Education & Learning Series – Digital Image Processing.**

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