Virtual Labs

Neighbourhood Operations

1. In a neighbourhood operation, the output value of a pixel depends on

a: Only the corresponding input pixel Explanation

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b: The pixel and its neighbouring pixels Explanation

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c: Only the image dimensions Explanation

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d: Only the image file format Explanation

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2. What is the purpose of a window or mask in a neighbourhood operation?

a: To select a local set of pixels around the current pixel Explanation

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b: To change the image file format Explanation

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c: To increase the image dimensions automatically Explanation

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d: To store the entire input image Explanation

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3. Which type of neighbourhood operation computes an output using a weighted combination of pixels in the local neighbourhood?

a: Nonlinear ranking operation Explanation

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b: Median operation Explanation

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c: Linear filtering operation Explanation

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d: File conversion operation Explanation

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4. A

3 \times 3

filter has all nine coefficients equal to

\frac{1}{9}

. What type of operation does this filter represent?

a: Median filtering Explanation

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b: Straight averaging filtering Explanation

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c: Unsharp masking Explanation

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d: Image thresholding Explanation

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5. If the size of an averaging neighbourhood is increased, the processed image will generally become

a: Smoother Explanation

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b: More dependent on only the centre pixel Explanation

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c: Converted into a binary image Explanation

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d: Unaffected by the neighbourhood size Explanation

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6. Which statement describes the median filter discussed in the Neighbourhood Operations experiment?

a: It computes a weighted sum of neighbourhood pixels Explanation

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b: It assigns the maximum gray value in the neighbourhood Explanation

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c: It uses only the centre pixel Explanation

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d: It computes the median of the gray values in the neighbourhood Explanation

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7. A low pass filter is used to smooth an image. According to the experiment, which property characterizes its filter coefficients?

a: Every coefficient is less than zero Explanation

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b: Every coefficient is greater than zero Explanation

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c: Every coefficient must be equal to zero Explanation

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d: The coefficients must alternate between positive and negative values Explanation

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8. Consider the linear neighbourhood operation

g(x,y) = \sum_{u=-a}^{a} \sum_{v=-b}^{b} w(u,v)f(x+u,y+v)

. What does

w(u,v)

represent?

a: The output image size Explanation

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b: The input image dimensions Explanation

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c: The filter coefficient or weight at a neighbourhood location Explanation

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d: The coordinates of the output image only Explanation

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9. Why is a special method needed when a neighbourhood window reaches the border of an image?

a: Some pixels required by the window lie outside the defined image Explanation

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b: The centre pixel becomes automatically brighter Explanation

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c: The filter coefficients become undefined Explanation

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d: The image must always be converted to a colour image Explanation

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