## Digital Electronic MCQ Set 1

1. Which of the following is/are more commercially successful image enhancement method in mask mode radiography, an area under medical imaging?

a) Addition

b) Subtraction

c) Multiplication

d) Division

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2. The subtraction operation results in areas that appear as dark shades of gray. Why?

a) Because the difference in such areas is little, that yields low value

b) Because the difference in such areas is high, that yields low value

c) Because the difference in such areas is high, that yields high value

d) None of the mentioned

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3. If the images are displayed using 8-bits, then, what is the range of the value of an image if the image is a result of subtraction operation?

a) 0 to 255

b) 0 to 511

c) -255 to 0

d) None of the mentioned

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_{i}nimum to 255 max

_{i}mum, if 8-bit channel is used to display the original images.

4. The subtracted image needs to be scaled, if 8-bit channel is used to display the subtracted images. So, the method of adding 255 to each pixel and then dividing by 2, has certain lim _{i}ts. What is/are those lim _{i}ts?

a) Very complex method

b) Very difficult to implement

c) The truncation inherent in division by 2 causes loss in accuracy

d) All of the mentioned

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_{i}tation of accuracy loss because of truncation inherent in division by 2 and also that it doesn’t ensure the full range usage.

5. Which of the following is/are the fundamental factors that need tight control for difference based inspection work?

a) Proper registration

b) Controlled illum _{i}nation

c) Noise levels should be low enough so that the variation due to noise won’t affect the difference value much

d) All of the mentioned

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_{i}nation is important because changes in illum

_{i}nation can affect dramatically the difference image values. Noise levels of a difference image must low enough so that the variation due to noise won’t affect the difference value much.

6. When can two random variables be uncorrelated?

a) Their covariance is 0

b) Their covariance is 1

c) Their covariance is -1

d) None of the mentioned

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_{i}and x

_{j}given by: E [(x

_{i}– m

_{i}) (x

_{j}– m

_{j})], E {.} is expected value of the argument and m is the mean. If this covariance turns out to 0, the variables are uncorrelated.

7. In Image Averaging enhancement method assumptions are made for a noisy image g(x, y). What is/are those?

a) The noise is correlated at every pair of coordinate (x, y)

b) The noise has average value 1 at every pair of coordinate (x, y)

c) All of the mentioned

d) None of the mentioned

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8. The standard deviation ‘σ’ at any point in image averaging: σ_{ḡ(x, y)} = 1/√K σ_{ɳ(x, y)}, where ḡ(x, y) is the average image formed by averaging K different noisy images and ɳ(x, y) is the noise added to an original image f(x, y). What is the relation between K and the variability of the pixel values at each location (x, y)?

a) Increase in K, decreases the noise of pixel values

b) Increase in K, increases the noise of pixel values

c) Decrease in K, decreases the noise of pixel values

d) Decrease in K, increases the noise of pixel values

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## Digital Electronic MCQ Set 2

1. Logic operations between two or more images are performed on pixel-by-pixel basis, except for one that is performed on a single image. Which one is that?

a) AND

b) OR

c) NOT

d) None of the mentioned

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2. Which of the following logical operator(s) is/are functionally complete?

a) AND

b) OR

c) NOT

d) All of the mentioned

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3. While implementing logic operation on gray-scale images, the processing of pixel values is done as ____

a) String of integer numbers

b) String of floating numbers

c) String of binary numbers

d) None of the mentioned

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4. What is the equivalent for a black, 8-bit pixel to be processed under logic operation on gray scale image?

a) A string: 00000000

b) A string: 11111111

c) A string: 10000000

d) A string: 01111111

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5. Which of the following operation(s) is/are equivalent to negative transformation?

a) AND

b) OR

c) NOT

d) All of the mentioned

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6. Which of the following operations are used for masking?

a) AND, OR

b) AND, NOT

c) NOT, OR

d) All of the mentioned

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7. Two images having one pixel gray value 01010100 and 00000101 at the same location, are operated against AND operator. What would be the resultant pixel gray value at that location in the enhanced image?

a) 10100100

b) 11111011

c) 00000100

d) 01010101

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8. Which of the following arithmetic operator is primarily used as a masking operator in enhancement?

a) Addition

b) Subtraction

c) Multiplication

d) Division

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## Digital Electronic MCQ Set 3

1. The expression [∂^{2} f(x,y)/∂x^{2} +∂^{2} f(x,y)/∂y^{2}] is considered as ___ where f(x, y) is an input image.

a) Laplacian of f(x, y)

b) Gradient of f(x, y)

c) All of the mentioned

d) None of the mentioned

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^{2}f=∂

^{2}f/∂x

^{2}+ ∂

^{2}f/∂y

^{2}.

2. If the Laplacian in frequency domain is: where is the Fourier transform operator and F(u, v) is Fourier transformed function of f(x, y), then what is -(u^{2}+ v^{2}) is considered as?

a) Laplacian operation

b) Filtering operation

c) Shift operation

d) None of the mentioned

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^{2}+ v

^{2}).

3. The Laplacian in frequency domain is simply implemented by using filter ____

a) H(u, v)= -(u^{2}– v^{2})

b) H(u, v)= -(1)

c) H(u, v)= -(u^{2}+ v^{2})

d) none of the mentioned

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^{2}f(x,y))/∂x

^{2}+(∂

^{2}f(x,y))/∂y

^{2}]= -(u

^{2}+v

^{2})F(u,v), where ℑ is the Fourier transform operator and F(u, v) is Fourier transformed function of f(x, y) and -(u

^{2}+ v

^{2}) is the filter.

4. Assuming that the origin of F(u, v), Fourier transformed function of f(x, y) an input image, has been correlated by performing the operation f(x, y)(-1)x+y prior to taking the transform of the image. If F and f are of same size, then what does the given operation is/are supposed to do?

a) Resize the transform

b) Rotate the transform

c) Shifts the center transform

d) All of the mentioned

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5. Assuming that the origin of F(u, v), Fourier transformed function of f(x, y) an input image, has been correlated by performing the operation f(x, y)(-1)x+y prior to taking the transform of the image. If F and f are of same size M*N, where does the point (u, v) =(0,0) shifts?

a) (M -1, N -1)

b) (M/2, N/2)

c) (M+1, N+1)

d) (0, 0)

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6. Assuming that the origin of F(u, v), Fourier transformed function of f(x, y) an input image, has been correlated by performing the operation f(x, y)(-1)x+y prior to taking the transform of the image. If F and f are of same size M*N, then which of the following is an expression for H(u, v), the filter used for implementing Laplacian in frequency domain?

a) H(u, v)= -(u^{2}+ v^{2})

b) H(u, v)= -(u^{2}– v^{2})

c) H(u, v)= -[(u – M/2)^{2}+ (v – N/2)^{2}].

d) H(u, v)= -[(u – M/2)^{2}– (v – N/2)^{2}].

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^{2}+ (v – N/2)

^{2}].

7. Computing the Fourier transform of the Laplacian result in spatial domain is equivalent to multiplying the F(u, v), Fourier transformed function of f(x, y) an input image, and H(u, v), the filter used for implementing Laplacian in frequency domain. This dual relationship is expressed as ___

a) Fourier transform pair notation

b) Laplacian

c) Gradient

d) None of the mentioned

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^{2}f(x,y)-[(u – M/2)

^{2}+ (v – N/2)

^{2}]F(u,v), for an image of size M *N.

8. Computing the Fourier transform of the Laplacian result in spatial domain is equivalent to multiplying the F(u, v), Fourier transformed function of f(x, y) an input image of size M*N, and H(u, v), the filter used for implementing Laplacian in frequency domain. This dual relationship is expressed as Fourier transform pair notation given by_______

a) ∇^{2} f(x,y)↔[(u –M/2)^{2}+ (v –N/2)^{2}]F(u,v)

b) ∇^{2} f(x,y)↔-[(u+M/2)^{2}– (v+N/2)^{2}]F(u,v)

c) ∇^{2} f(x,y)↔-[(u –M/2)^{2}+ (v –N/2)^{2}]F(u,v)

d) ∇^{2} f(x,y)↔[(u+M/2)^{2}– (v+N/2)^{2}]F(u,v)

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^{2}f(x,y)↔-[(u – M/2)

^{2}+ (v – N/2)

^{2}]F(u,v), for an image of size M*N.

9. An enhanced image can be obtained as: g(x,y)=f(x,y)-∇^{2} f(x,y), where Laplacian is being subtracted from f(x, y) the input image. What does this conclude?

a) That the center spike would be negative

b) That the immediate neighbors of center spike would be positive.

c) All of the mentioned

d) None of the mentioned

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10. An enhanced image can be obtained as: g(x,y)=f(x,y)-∇^{2} f(x,y), where Laplacian is being subtracted from f(x, y) the input image of size M*Non which an operation f(x, y)(-1)x+yis applied.Unlike enhancing in spatial domain with one single mask, it is possible to perform the same in frequency domain using one filter. Which of the following is/are the required filter(s)?

a) H(u, v)= -[1 + u^{2}+ v^{2}].

b) H(u, v)= -[(u – M/2)2+ (v– N/2)2].

c) H(u, v)= [1 + (u – M/2)2+ (v – N/2)2].

d) All of the mentioned

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11. Why is scaling of Laplacian filtered images necessary?

a) Because it contain high positive values

b) Because it contain high negative value

c) Because it contain both positive and negative values

d) None of the mentioned

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12. Which of the following fact is true for the masks that includes diagonal neighbors than the masks that doesn’t?

a) Mask that excludes diagonal neighbors has more sharpness than the masks that doesn’t

b) Mask that includes diagonal neighbors has more sharpness than the masks that doesn’t

c) Both masks have same sharpness result

d) None of the mentioned

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## Digital Electronic MCQ Set 4

1. Which of the following fact(s) is/are true for the relationship between low frequency component of Fourier transform and the rate of change of gray levels?

a) Moving away from the origin of transform the low frequency corresponds to smooth gray level variation

b) Moving away from the origin of transform the low frequencies corresponds to abrupt change in gray level

c) All of the mentioned

d) None of the mentioned

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2. Which of the following fact(s) is/are true for the relationship between high frequency component of Fourier transform and the rate of change of gray levels?

a) Moving away from the origin of transform the high frequency corresponds to smooth gray level variation

b) Moving away from the origin of transform the higher frequencies corresponds to abrupt change in gray level

c) All of the mentioned

d) None of the mentioned

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3. What is the name of the filter that multiplies two functions F(u, v) and H(u, v), where F has complex components too since is Fourier transformed function of f(x, y), in an order that each component of H multiplies both real and complex part of corresponding component in F?

a) Unsharp mask filter

b) High-boost filter

c) Zero-phase-shift-filter

d) None of the mentioned

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4. To set the average value of an image zero, which of the following term would be set 0 in the frequency domain and the inverse transformation is done, where F(u, v) is Fourier transformed function of f(x, y)?

a) F(0, 0)

b) F(0, 1)

c) F(1, 0)

d) None of the mentioned

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5. What is the name of the filter that is used to turn the average value of a processed image zero?

a) Unsharp mask filter

b) Notch filter

c) Zero-phase-shift-filter

d) None of the mentioned

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6. Which of the following filter(s) attenuates high frequency while passing low frequencies of an image?

a) Unsharp mask filter

b) Lowpass filter

c) Zero-phase-shift filter

d) All of the mentioned

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7. Which of the following filter(s) attenuates low frequency while passing high frequencies of an image?

a) Unsharp mask filter

b) Highpass filter

c) Zero-phase-shift filter

d) All of the mentioned

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8. Which of the following filter have a less sharp detail than the original image because of attenuation of high frequencies?

a) Highpass filter

b) Lowpass filter

c) Zero-phase-shift filter

d) None of the mentioned

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9. The feature(s) of a highpass filtered image is/are _____

a) Have less gray-level variation in smooth areas

b) Emphasized transitional gray-level details

c) An overall sharper image

d) All of the mentioned

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10. A spatial domain filter of the corresponding filter in frequency domain can be obtained by applying which of the following operation(s) on filter in frequency domain?

a) Fourier transform

b) Inverse Fourier transform

c) None of the mentioned

d) All of the mentioned

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11. A frequency domain filter of the corresponding filter in spatial domain can be obtained by applying which of the following operation(s) on filter in spatial domain?

a) Fourier transform

b) Inverse Fourier transform

c) None of the mentioned

d) All of the mentioned

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12. Which of the following filtering is done in frequency domain in correspondence to lowpass filtering in spatial domain?

a) Gaussian filtering

b) Unsharp mask filtering

c) High-boost filtering

d) None of the mentioned

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13. Using the feature of reciprocal relationship of filter in spatial domain and corresponding filter in frequency domain, which of the following fact is true?

a) The narrower the frequency domain filter results in increased blurring

b) The wider the frequency domain filter results in increased blurring

c) The narrower the frequency domain filter results in decreased blurring

d) None of the mentioned

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## Digital Electronic MCQ Set 5

1. Smoothing in frequency domain is achieved by attenuating which of the following component in the transform of a given image?

a) Attenuating a range of high-frequency components

b) Attenuating a range of low-frequency components

c) All of the mentioned

d) None of the mentioned

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2. Which of the following is/are considered as type(s) of lowpass filters?

a) Ideal

b) Butterworth

c) Gaussian

d) All of the mentioned

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3. Which of the following lowpass filters is/are covers the range of very sharp filter function?

a) Ideal lowpass filters

b) Butterworth lowpass filter

c) Gaussian lowpass filter

d) All of the mentioned

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4. Which of the following lowpass filters is/are covers the range of very smooth filter function?

a) Ideal lowpass filters

b) Butterworth lowpass filter

c) Gaussian lowpass filter

d) All of the mentioned

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5. Butterworth lowpass filter has a parameter, filter order, determining its functionality as very sharp or very smooth filter function or an intermediate filter function. If the parameter value is very high, the filter approaches to which of the following filter(s)?

a) Ideal lowpass filter

b) Gaussian lowpass filter

c) All of the mentioned

d) None of the mentioned

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6. Butterworth lowpass filter has a parameter, filter order, determining its functionality as very sharp or very smooth filter function or an intermediate filter function. If the parameter value is of lower order, the filter approaches to which of the following filter(s)?

a) Ideal lowpass filter

b) Gaussian lowpass filter

c) All of the mentioned

d) None of the mentioned

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7. In a filter, all the frequencies inside a circle of radius D0 are not attenuated while all frequencies outside circle are completely attenuated. The D0 is the specified nonnegative distance from origin of the Fourier transform. Which of the following filter(s) characterizes the same?

a) Ideal filter

b) Butterworth filter

c) Gaussian filter

d) All of the mentioned

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8. In an ideal lowpass filter case, what is the relation between the filter radius and the blurring effect caused because of the filter?

a) Filter size is directly proportional to blurring caused because of filter

b) Filter size is inversely proportional to blurring caused because of filter

c) There is no relation between filter size and blurring caused because of it

d) None of the mentioned

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9. The characteristics of the lowpass filter h(x, y) is/are___

a) Has a dominant component at origin

b) Has a concentric, circular components about the center component

c) All of the mentioned

d) None of the mentioned

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10. What is the relation for the components of ideal lowpass filter and the image enhancement?

a) The concentric component is primarily responsible for blurring

b) The center component is primarily for the ringing characteristic of ideal filter

c) All of the mentioned

d) None of the mentioned

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11. Using the feature of reciprocal relationship of filter in spatial domain and corresponding filter in frequency domain along with convolution, which of the following fact is true?

a) The narrower the frequency domain filter more severe is the ringing

b) The wider the frequency domain filter more severe is the ringing

c) The narrower the frequency domain filter less severe is the ringing

d) None of the mentioned

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12. Which of the following defines the expression for BLPF H(u, v) of order n, where D(u, v) is the distance from point (u, v), D0 is the distance defining cutoff frequency?

a)

b)

c) All of the mentioned

d) None of the mentioned

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13. Which of the following defines the expression for ILPF H(u, v) of order n, where D(u, v) is the distance from point (u, v), D0 is the distance defining cutoff frequency?

a)

b)

c) All of the mentioned

d) None of the mentioned

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14. State the statement true or false: “BLPF has sharp discontinuity and ILPF doesn’t, and so ILPF establishes a clear cutoff b/w passed and filtered frequencies”.

a) True

b) False

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15. A Butterworth filter of what order has no ringing?

a) 1

b) 2

c) 3

d) 4