81. Which of the following operations are used for masking?
A. AND, OR
B. AND, NOT
C. NOT, OR
D. All of Mentioned
Answer: C
AND, OR operators are used for masking, while NOT works as negative transformation.
82. Two images having one-pixel gray values 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
Answer: C
For AND operation results in 1 only for 1AND 1, else 0. All the bits of the given gray value are operated similarly resulting in 00000100.
83. Which of the following arithmetic operator is primarily used as a masking operator in enhancement?
A. Addition
B. Subtraction
C. Multiplication
D. Division
Answer: C
The multiplication arithmetic operator is primarily used as a masking operator in enhancement. Multiplication of one image by another is used as a gray-level mask.
84. Which of the following is/are the more commercially successful image enhancement method in mask mode radiography, an area under medical imaging?
A. Addition
B. Subtraction
C. Multiplication
D. Division
Answer: B
In the given area of medical imaging, a mask of an X-ray image of a region of the subject is captured using a TV camera and is subtracted from an image of the same region taken after injecting a contrast medium into the bloodstream. The subtraction result gives an enhanced detail of how a contrast medium propagates through the bloodstream.
This is the best commercially successful method.
85. Why does the subtraction operation results in areas that appear as dark shades of gray?
A. Because the difference in such areas is little, that yields a low value
B. Because the difference in such areas is high, that yields a low value
C. Because the difference in such areas is high, that yields a high value
D. None of the mentioned
Answer: A
The subtraction operation results in areas that appear as dark shades of gray because the difference in such areas is little, which yields a low value.
There remains a little change in some areas in the images to be subtracted that yields low value and so the result appears as dark shades of gray.
86. 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 a subtraction operation?
A. 0 to 255
B. 0 to 511
C. -255 to 0
D. None of the mentioned
Answer: D
The range of a result of a subtracted image is -255 minimum to 255 maximum if the 8-bit channel is used to display the original images.
87. The subtracted image needs to be scaled if the 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 limits. What is/are those limits?
A. Very complex method
B. Very difficult to implement
C. The truncation inherent in the division by 2 causes a loss of inaccuracy
D. All of Mentioned
Answer: C
The truncation inherent method is quite simple and easy to implement, however, it has the limitation of accuracy loss because of truncation inherent in the division by 2 and also that it doesn’t ensure the full range usage.
88. Which of the following are/are the fundamental factors that need tight control for difference-based inspection work?
A. Proper registration
B. Controlled illumination
C. Noise levels should be low enough so that the variation due to noise won’t affect the difference value much
D. All of Mentioned
Answer: D
Proper Registration does special marking into the product in case two images are identical, so the difference won’t create any sense.
Controlled Illumination is important because changes in illumination can affect dramatically the difference in image values.
Noise levels of a difference image must be low enough so that the variation due to noise won’t affect the difference value much.
89. 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
Answer: A
The covariance of two random variables x i and x j given by: E [(x i – m i) (x j – mj)], E {.} is the expected value of the argument and m is the mean. If this covariance turns out to be 0, the variables are uncorrelated.
90. What are Image Averaging enhancement methods in which assumptions are made for a noisy image g(x, y)?
A. The noise is correlated at every pair of coordinates (x, y)
B. The noise has an average value of 1 at every pair of coordinates (x, y)
C. All of Mentioned
D. None of the mentioned
Answer: D
In Image, Averaging enhancement method assumptions are made for a noisy image g(x, y) that at every coordinate (x, y) the noise has 0 average value and must be uncorrelated.
