How can one reduce the aliasing effect on an image?

DIGITAL IMAGE PROCESSING (DIP) - IMAGE ENHANCEMENT MCQ

• The principal factor to determine the spatial resolution of an image is _______
• What causes the effect, imperceptible set of very fine ridge like structures in areas of smooth gray levels?
• What is the name of the effect caused by the use of an insufficient number of gray levels in smooth areas of a digital image?
• Using rough rule of thumb, and assuming powers of 2 for convenience, what image size are about the smallest images that can be expected to be reasonably free of objectionable sampling checkerboards and false contouring?
• What does a shift up and right in the curves of isopreference curve simply means? Verify in terms of N (number of pixels) and k (L=2k, L is the gray level) values
• How does the curves behave to the detail in the image in isopreference curve?
• For an image with a large amount of detail, if the value of N (number of pixels) is fixed then what is the gray level dependency in the perceived quality of this type of image?
• What is a band-limited function?
• For a band-limited function, which Theorem says that “if the function is sampled at a rate equal to or greater than twice its highest frequency, the original function can be recovered from its samples”?
• What is the name of the phenomenon that corrupts the sampled image, and how does it happen?
• How aliasing does corrupts the sampled image?
• How can one reduce the aliasing effect on an image?
• In terms of Sampling and Quantization, Zooming and Shrinking may be viewed as ___________
• The two steps: one is the creation of new pixel locations, and other is the assignment of gray levels to those new locations are involved in ____________
• While Zooming, In order to perform gray-level assignment for any point in the overlay, we assign its gray level to the new pixel in the grid its closest pixel in the original image. What’s this method of gray-level assignment called?
• A special case of nearest neighbor Interpolation that just duplicates the pixels the number of times to achieve the desired size, is known as ___________
• Nearest neighbor Interpolation has an undesirable feature, that is _________
• What does the bilinear Interpolation do for gray-level assignment?
• Row-column deletion method of Image Shrinking is an equivalent process to which method of Zooming?
• Image Shrinking has an undesirable feature, that is ____________
• State for the validation of the statement:
• A pixel p at coordinates (x, y) has neighbors whose coordinates are given by: (x+1, y), (x-1, y), (x, y+1), (x, y-1) This set of pixels is called ____________
• A pixel p at coordinates (x, y) has neighbors whose coordinates are given by: (x+1, y+1), (x+1, y-1), (x-1, y+1), (x-1, y-1) This set of pixels is called ____________
• What is the set of pixels of 8-neighbors of pixel p at coordinates (x, y)?
• Two pixels p and q having gray values from V, the set of gray-level values used to define adjacency, are m-adjacent if:
• Let S, a subset of pixels in an image, is said to be a connected set if:
• Let R be a subset of pixels in an image. How can we define the contour of R?
• The domain that refers to image plane itself and the domain that refers to Fourier transform of an image is/are :
• What is the technique for a gray-level transformation function called, if the transformation would be to produce an image of higher contrast than the original by darkening the levels below some gray-level m and brightening the levels above m in the original image
• For Image Enhancement a general-approach is to use a function of values of f (input image) in a predefined neighborhood of (x, y) to determine the value of g (output image) at (x, y). The techniques that uses such approaches are called ________
• Using gray-level transformation, the basic function linearity deals with which of the following transformation?
• Using gray-level transformation, the basic function Logarithmic deals with which of the following transformation?
• Using gray-level transformation, the basic function power-law deals with which of the following transformation?
• If r be the gray-level of image before processing and s after processing then which expression defines the negative transformation, for the gray-level in the range [0, L-1]?
• If r be the gray-level of image before processing and s after processing then which expression helps to obtain the negative of an image for the gray-level in the range [0, L-1]?
• If r be the gray-level of image before processing and s after processing then which expression defines the power-law transformation, for the gray-level in the range [0, L-1]?
• Which of the following transformations is particularly well suited for enhancing an image with white and gray detail embedded in dark regions of the image, especially when there is more black area in the image
• Which of the following transformations expands the value of dark pixels while the higher-level values are being compressed?
• Although power-law transformations are considered more versatile than log transformations for compressing of gray-levels in an image, then, how is log transformations advantageous over power-law transformations?
• A typical Fourier Spectrum with spectrum value ranging from 0 to 106, which of the following transformation is better to apply
• The power-law transformation is given as: s = crᵞ, c and ᵞ are positive constants, and r is the gray-level of image before processing and s after processing. Then, for what value of c and ᵞ does power-law transformation becomes identity transformation?
• Which of the following transformation is used cathode ray tube (CRT) devices?
• Log transformation is generally used in which of the following device(s)?
• The power-law transformation is given as: s = crᵞ, c and ᵞ are positive constants, and r is the gray-level of image before processing and s after processing. What happens if we increase the gamma value from 0.3 to 0.7?
• If h(rk) = nk, rk the kth gray level and nk total pixels with gray level rk, is a histogram in gray level range [0, L – 1]. Then how can we normalize a histogram?
• What is the sum of all components of a normalized histogram?
• A low contrast image will have what kind of histogram when, the histogram, h(rk) = nk, rk the kth gray level and nk total pixels with gray level rk, is plotted nk versus rk?
• A bright image will have what kind of histogram, when the histogram, h(rk) = nk, rk the kth gray level and nk total pixels with gray level rk, is plotted nk versus rk?
• The transformation s = T(r) producing a gray level s for each pixel value r of input image. Then, if the T(r) is single valued in interval 0 ≤ r ≤ 1, what does it signifies?
• The transformation s = T(r) producing a gray level s for each pixel value r of input image. Then, if the T(r) is monotonically increasing in interval 0 ≤ r ≤ 1, what does it signifies?
• The transformation s = T(r) producing a gray level s for each pixel value r of input image. Then, if the T(r) is satisfying 0 ≤ T(r) ≤ 1 in interval 0 ≤ r ≤ 1, what does it signifies?
• What is the full form for PDF, a fundamental descriptor of random variables i.e. gray values in an image?
• What is the full form of CDF?
• For the transformation T(r) = [∫0^r pr(w) dw], r is gray value of input image, pr(r) is PDF of random variable r and w is a dummy variable. If, the PDF are always positive and that the function under integral gives the area under the function, the transformation is said to be __________
• The transformation T (rk) = ∑k(j=0) nj /n, k = 0, 1, 2, …, L-1, where L is max gray value possible and r-k is the kth gray level, is called _______
• If the histogram of same images, with different contrast, are different, then what is the relation between the histogram equalized images?
• The technique of Enhancement that has a specified Histogram processed image as result, is called?
• In Histogram Matching r and z are gray level of input and output image and p stands for PDF, then, what does pz(z) stands for?
• Inverse transformation plays an important role in which of the following Histogram processing Techniques?
• In Histogram Matching or Specification, z = G^-1[T(r)], r and z are gray level of input and output image and T & G are transformations, to confirm the single value and monotonous of G^-1 what of the following is/are required?
• Which of the following histogram processing techniques is global?
• What happens to the output image when global Histogram equalization method is applied on smooth and noisy area of an image?
• In terms of enhancement, what does mean and variance refers to?
• What is standard deviation value for constant area?
• For a local enhancement using mean and variance, what happens if the lowest value of contrast is not restricted as per the willingness of acceptance of value?
• 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?
• Which of the following logical operator(s) is/are functionally complete?
• While implementing logic operation on gray-scale images, the processing of pixel values is done as __________
• What is the equivalent for a black, 8-bit pixel to be processed under logic operation on gray scale image?
• Which of the following operation(s) is/are equivalent to negative transformation?
• Which of the following operations are used for masking?
• 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?
• Which of the following arithmetic operator is primarily used as a masking operator in enhancement?
• Which of the following is/are more commercially successful image enhancement method in mask mode radiography, an area under medical imaging?
• The subtraction operation results in areas that appear as dark shades of gray. Why?
• 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?
• 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 limits. What is/are those limits?
• Which of the following is/are the fundamental factors that need tight control for difference based inspection work?
• When can two random variables be uncorrelated?
• In Image Averaging enhancement method assumptions are made for a noisy image g(x, y). What is/are those?
• The standard deviation ‘σ’ at any point in image averaging:
• A filter is applied to an image whose response is independent of the direction of discontinuities in the image. The filter is/are ________
• In isotropic filtering, which of the following is/are the simplest isotropic derivative operator?
• The Laplacian is which of the following operator?
• The Laplacian ∇^2 f=[f(x + 1, y) + f(x – 1, y) + f(x, y + 1) + f(x, y – 1) – 4f(x, y)], gives an isotropic result for rotations in increment by what degree?
• The Laplacian incorporated with diagonal directions, i.e. ∇^2 f=[f(x + 1, y) + f(x – 1, y) + f(x, y + 1) + f(x, y – 1) – 8f(x, y)], gives an isotropic result for rotations in increment by what degree?
• Applying Laplacian has which of the following result(s)?
• Applying Laplacian produces image having featureless background which is recovered maintaining the sharpness of Laplacian operation by either adding or subtracting it from the original image depending upon the Laplacian definition used. Which of the following is true based on above statement?
• A mask of size 3*3 is formed using Laplacian including diagonal neighbors that has central coefficient as 9. Then, what would be the central coefficient of same mask if it is made without diagonal neighbors?
• Which of the following mask(s) is/are used to sharpen images by subtracting a blurred version of original image from the original image itself?
• Which of the following gives an expression for high boost filtered image fhb,
• If we use a Laplacian to obtain sharp image for unsharp mask filtered image fs(x, y) of f(x, y) as input image
• “For very large value of A, a high boost filtered image is approximately equal to the original image”. State whether the statement is true or false?
• Subtracting Laplacian from an image is proportional to which of the following?
• A First derivative in image processing is implemented using which of the following given operator(s)?
• What is the sum of the coefficient of the mask defined using gradient?
• Gradient is used in which of the following area(s)?
• Gradient have some important features. Which of the following is/are some of them?
• An image has significant edge details. Which of the following fact(s) is/are true for the gradient image and the Laplacian image of the same?
• The Laplacian in frequency domain is simply implemented by using filter __________
• Assuming that the origin of F(u, v)
• Assuming that the origin of F(u, v),
• Assuming that the origin of F(u, v),
• Computing the Fourier transform of the Laplacian result in spatial domain is equivalent to multiplying the F(u, v)
• 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?
• Why is scaling of Laplacian filtered images necessary?
• Which of the following fact is true for the masks that includes diagonal neighbors than the masks that doesn’t?

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