# Digital Image Processing Questions and Answers – Homomorphic filtering

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This set of Digital Image Processing Questions and Answers for Campus interviews focuses on “Homomorphic filtering-2”.

1. Which of the following fact is true for a image?
a) An image is the addition of illumination and reflectance component
b) An image is the subtraction of illumination component from reflectance component
c) An image is the subtraction of reflectance component from illumination component
d) An image is the multiplication of illumination and reflectance component

Explanation: An image is expressed as the multiplication of illumination and reflectance component.

2. If an image is expressed as the multiplication of illumination and reflectance component i.e. f(x, y)= i(x, y) * r(x, y), then Validate the statement “We can directly use the equation f(x, y)= i(x, y) * r(x, y) to operate separately on the frequency component of illumination and reflectance” .
a) True
b) False

Explanation: For an image is expressed as the multiplication of illumination and reflectance component i.e. f(x, y)= i(x, y) * r(x, y), the equation can’t be used directly to operate separately on the frequency component of illumination and reflectance because the Fourier transform of the product of two function is not separable.

3. In Homomorphic filtering which of the following operations is used to convert input image to discrete Fourier transformed function?
a) Logarithmic operation
b) Exponential operation
c) Negative transformation
d) None of the mentioned

Explanation: For an image is expressed as the multiplication of illumination and reflectance component i.e. f(x, y) = i(x, y) * r(x, y), the equation can’t be used directly to operate separately on the frequency component of illumination and reflectance because the Fourier transform of the product of two function is not separable. So, the logarithmic operation is used.I{z(x,y)}=I{ln⁡(f(x,y)) }=I{ln⁡(i(x,y)) }+I{ln⁡(r(x,y))}.
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4. A class of system that achieves the separation of illumination and reflectance component of an image is termed as __________
a) Base class system
b) Homomorphic system
c) Base separation system
d) All of the mentioned

Explanation: Homomorphic system is a class of system that achieves the separation of illumination and reflectance component of an image.

5. Which of the following image component is characterized by a slow spatial variation?
a) Illumination component
b) Reflectance component
c) All of the mentioned
d) None of the mentioned

Explanation: The illumination component of an image is characterized by a slow spatial variation.

6. Which of the following image component varies abruptly particularly at the junction of dissimilar objects?
a) Illumination component
b) Reflectance component
c) All of the mentioned
d) None of the mentioned

Explanation: The reflectance component of an image varies abruptly particularly at the junction of dissimilar objects.

7. The reflectance component of an image varies abruptly particularly at the junction of dissimilar objects. The characteristic lead to associate illumination with __________
a) The low frequency of Fourier transform of logarithm of the image
b) The high frequency of Fourier transform of logarithm of the image
c) All of the mentioned
d) None of the mentioned

Explanation: The reflectance component of an image varies abruptly, so, is associated with the high frequency of Fourier transform of logarithm of the image.

8. The illumination component of an image is characterized by a slow spatial variation. The characteristic lead to associate illumination with __________
a) The low frequency of Fourier transform of logarithm of the image
b) The high frequency of Fourier transform of logarithm of the image
c) All of the mentioned
d) None of the mentioned

Explanation: The illumination component of an image is characterized by a slow spatial variation, so, is associated with the low frequency of Fourier transform of logarithm of the image.

9. If the contribution made by illumination component of image is decreased and the contribution of reflectance component is amplified, what will be the net result?
a) Dynamic range compression
b) Contrast enhancement
c) All of the mentioned
d) None of the mentioned

Explanation: The illumination component of an image is characterized by a slow spatial variation and the reflectance component of an image varies abruptly particularly at the junction of dissimilar objects, so, if the contribution made by illumination component of image is decreased and the contribution of reflectance component is amplified then there is simultaneous dynamic range compression and contrast stretching.