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Indian Institute of Technology Kharagpur
Digital Image Processing
Assignment- Week 12
TYPE OF QUESTION: MCQ/MSQ
Number of questions: 10
Total mark: 10 X 1 = 10
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QUESTION 1:
The applications of segmentation is (are)______________________.
a.
b.
c.
d.
Detection of similar regions.
Detection of lines and edges in an image.
Both a and b.
None of the above mentioned.
Correct Answer: c.
Detailed Solution:
Segmentation is used to detect similar regions, lines and edges in an image,
Hence option c is correct.
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QUESTION 2:
Which of the following are major point of interest in discontinuity based segmentation
algorithms?
a.
b.
c.
d.
Isolated points
Lines
Edges
All of the above
Correct Answer: d.
Detailed Solution:
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In discontinuity segmentation algorithms, isolated points, lines and edges are major point of
interest for segmentation.
Hence option d is correct.
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QUESTION 3:
A point (1,2) in the Cartesian system is represented in slope-intercept space  m, c  as
a. 𝑚 = −𝑐 + 2
b. 𝑚 = −2𝑐 + 2
c. 𝑐 = −2𝑚 + 2
d. None of the above
Correct Answer: a.
Detailed Solution:
Equation of line slope-intercept form is written as y  mx  c . Here  m, c  is Hough space,
Then the point (1,2) will be a line in hough space represented as 2 = 1𝑚 + 𝑐 or 𝑚 = −𝑐 + 2.
Hence option a is correct.
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QUESTION 4:
  1 0 1
Which of the following is (are) are true for horizontal Sobel operator, Gx   2 0 2 ?
  1 0 1
a. Perform averaging in vertical direction and differentiation in horizontal direction
b. Perform averaging in horizontal direction and differentiation in vertical direction
c. It can be used for detection vertical edges
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d. Both a and c
Correct Answer: a.
Detailed Solution:
1 
G y can be decomposed into two one dimensional operators as G y  2 *  1 0 1 .
 
1
This shows that it performs averaging in vertical direction and differentiation in horizontal
direction.
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QUESTION 5:
In a given image strip (S), assuming necessary zero padding find second order derivative
𝑆=2 2 2 2 2 2 0 0 0 0
a) −2 0 0 0 0 − 2 2 0 0 0
b) 2 0 0 0 0 2 − 2 0 0 0
c) −2 0 0 0 0 2 2 0 0 0
d) 2 0 0 0 0 2 2 0 0 0
Correct Answer: a.
Detailed Solution:
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Using the relation, f " ( x)  f ( x  1)  f ( x  1)  2 f ( x) . For example for f  0 ,
f  0  f 1  f  1  2 f  0 here f  1  0 , therefore𝑓(0) = 2 + 0 − 2 ∗ 2 = −2.
Similarly, 𝑓(1) = 𝑓(2) + 𝑓(0) − 2𝑓(1) = 2 + 2 − 2 ∗ 2 = 0.
In this way we can compute the second order derivative for this sequence.
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QUESTION 6:
Which of the following is an example of similarity-based approach in image segmentation?
a.
b.
c.
d.
Edge based segmentation
Region based segmentation
Boundary based segmentation
Both A and B
Correct Answer: b.
Detailed Solution:
Region based segmentation is an example of similarity based approach in image segmentation
Hence option b is correct.
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QUESTION 7:
Which of the following segmentation technique is supervised or semi-supervised?
a. Region growing
b. Splitting and merging
c. Thresholding
d. None of the above
Correct Answer: a.
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Indian Institute of Technology Kharagpur
Detailed Solution:
In case of region growing, we have to provide a seed point to start the segmentation. Therefore it’s
a supervised or semi-supervised segmentation technique.
Hence option a is correct.
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QUESTION 8:
Which of the following statements are true for Laplacian operator?
a) It can be used to find appropriate location of edge using zero crossings.
b) Sensitive to noise.
c) Both a and b
d) None of the above
Correct Answer: c.
Detailed Solution:
Lapalcian operator is a second order derivative operator and therefore can can be used to find
appropriate location of edge using zero crossings. But this second order derivative makes it
sensitive to noise.
Hence option c is correct.
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QUESTION 9:
A point in cartsian space is represented in Hough space (slope intercept space) as ___________
a. Point
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b. Straight line
c. Parabola
d. None of these
Correct Answer: b.
Detailed Solution:
Equation of line slope-intercept form in Cartesian space is written as y  mx  c .
Let
 m, c  is
Hough space and x0 , y 0  is a point in Cartesian space, then in Hough space
y 0  mx 0  c .
On simplification we write it as m  
y
1
c  0 , which represents a line in  m, c  space.
x0
x0
Hence option b is correct.
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QUESTION 10:
Which of the following is (are) Sobel operator?
A
−1 0 1
[−2 0 2]
−1 0 1
B
1
1
1
[0
0
0]
−1 −1 −1
C
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−1 0 1
[−1 0 1]
−1 0 1
D
1
2
1
[0
0
0]
−1 −2 −1
a. Only A
b. Only C
c. Both A and D
d. Both B and C
Correct Answer: c.
Detailed Solution:
−1 0 1
[−2 0 2] corresponds to horizontal Sobel filter and
−1 0 1
1
2
1
[0
0
0 ] corresponds to vertical Sobel filter.
−1 −2 −1
Hence option c is correct.
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