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1.	Which of the following statement(s) is true for the given fact that “Applying Highpass filters has an effect on the background of the output image”?(a) The average background intensity increases to near white(b) The average background intensity reduces to near black(c) The average background intensity changes to a value average of black and white(d) All of the mentionedThis question was posed to me in an interview for internship.This interesting question is from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in division Filtering in Frequency Domain of Digital Image Processing
Answer» Right option is (b) The average background intensity reduces to near BLACK Explanation: The Highpass filter eliminates the ZERO frequency components of the FOURIER transformed image HPFs are APPLIED on. So, the average background intensity reduces to near black.

2.	For a given image having smaller objects, which of the following filter(s), having D0 as the cutoff distance measured from origin of frequency rectangle, would you prefer for a comparably smoother result?(a) IHLF with D0 15(b) BHPF with D0 15 and order 2(c) GHPF with D0 15 and order 2(d) All of the mentionedI have been asked this question by my school teacher while I was bunking the class.This is a very interesting question from Gaussain Lowpass and Sharpening Frequency Domain Filters in division Filtering in Frequency Domain of Digital Image Processing
Answer» Right answer is (c) GHPF with D0 15 and order 2 To elaborate: For the same format as for BHPF, GHPF gives a RESULT comparably SMOOTHER than BHPF. However, BHPF PERFORMANCE for filtering SMALLER object is comparable with IHPF.

3.	What is the relation of the frequencies to a circle of radius D0, where D0 is the cutoff distance measured from origin of frequency rectangle, for an Ideal Highpass filter?(a) IHPF sets all frequencies inside circle to zero(b) IHPF allows all frequencies, without attenuating, outside the circle(c) All of the mentioned(d) None of the mentionedThe question was asked during an online exam.Question is taken from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in section Filtering in Frequency Domain of Digital Image Processing
Answer» Correct CHOICE is (C) All of the mentioned The explanation is: An Ideal high pass filter gives 0 for D(U, v) ≤ D0 and 1 for D(u, v) >D0.

4.	If D0 is the cutoff distance measured from origin of frequency rectangle and D(u, v) is the distance from point(u, v). Then what value does an Ideal Highpass filter will give if D(u, v) ≤ D0 andifD(u, v) >D0?(a) 0 and 1 respectively(b) 1 and 0 respectively(c) 1 in both case(d) 0 in both caseI had been asked this question in semester exam.This intriguing question comes from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in chapter Filtering in Frequency Domain of Digital Image Processing
Answer» Correct option is (a) 0 and 1 respectively Easiest EXPLANATION: Unlike Ideal lowpass filter, an Ideal highpass filter ATTENUATES the low-frequency components and so gives 0 for D(u, V) ≤ D0 and 1 for D(u, v) >D0.

5.	The function of filters in Image sharpening in frequency domain is to perform reverse operation of which of the following Lowpass filter?(a) Gaussian Lowpass filter(b) Butterworth Lowpass filter(c) Ideal Lowpass filter(d) None of the MentionedI got this question by my school teacher while I was bunking the class.This interesting question is from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in division Filtering in Frequency Domain of Digital Image Processing
Answer» Correct answer is (C) IDEAL Lowpass filter Best EXPLANATION: The function of filters in Image sharpening in frequency domain is to perform precisely reverse OPERATION of Ideal Lowpass filter. The transfer function of Highpass filter is obtained by relation: Hhp(U, v) = 1 – Hlp(u, v), where Hlp(u, v) is transfer function of corresponding lowpass filter.

6.	The Image sharpening in frequency domain can be achieved by which of the following method(s)?(a) Attenuating the high frequency components(b) Attenuating the low-frequency components(c) All of the mentioned(d) None of the mentionedThe question was asked during an interview.The origin of the question is Gaussain Lowpass and Sharpening Frequency Domain Filters in chapter Filtering in Frequency Domain of Digital Image Processing
Answer» The correct OPTION is (b) ATTENUATING the low-frequency components Explanation: The Image SHARPENING in frequency domain is ACHIEVED by attenuating the low-frequency components without DISTURBING the high-frequency components.

7.	A type of Image is called as VHRR image. What is the definition of VHRR image?(a) Very High Range Resolution image(b) Very High Resolution Range image(c) Very High Resolution Radiometer image(d) Very High Range Radiometer ImageThis question was addressed to me in an interview for job.Query is from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in chapter Filtering in Frequency Domain of Digital Image Processing
Answer» RIGHT ANSWER is (C) Very HIGH Resolution Radiometer image Explanation: A VHRR image is a Very High Resolution Radiometer Image.

8.	The edges and other abrupt changes in gray-level of an image are associated with_________(a) High frequency components(b) Low frequency components(c) Edges with high frequency and other abrupt changes in gray-level with low frequency components(d) Edges with low frequency and other abrupt changes in gray-level with high frequency componentsI have been asked this question in semester exam.I'd like to ask this question from Gaussain Lowpass and Sharpening Frequency Domain Filters in chapter Filtering in Frequency Domain of Digital Image Processing
Answer» CORRECT CHOICE is (a) High FREQUENCY components To explain: High frequency components are related with the EDGES and other abrupt CHANGES in gray-level of an image.

9.	State the statement as true or false. “The GLPF did produce as much smoothing as the BLPF of order 2 for the same value of cutoff frequency”.(a) True(b) FalseI have been asked this question in quiz.Origin of the question is Gaussain Lowpass and Sharpening Frequency Domain Filters topic in section Filtering in Frequency Domain of Digital Image Processing
Answer» Correct OPTION is (b) False To explain: For the same value of cutoff frequency, the GLPF did not PRODUCE as much SMOOTHING as the BLPF of order 2, because the profile of GLPF is not as tight as BLPF of order 2.

10.	The lowpass filtering process can be applied in which of the following area(s)?(a) The field of machine perception, with application of character recognition(b) In field of printing and publishing industry(c) In field of processing satellite and aerial images(d) All of the mentionedThe question was asked in unit test.My doubt is from Gaussain Lowpass and Sharpening Frequency Domain Filters in division Filtering in Frequency Domain of Digital Image Processing
Answer» CORRECT choice is (d) All of the mentioned For explanation I would say: In case of broken CHARACTERS RECOGNITION system, LPF is used. LPF is used as preprocessing system in printing and publishing industry, and in case of remote sensed images LPF is used to blur out as much detail as POSSIBLE leaving the LARGE feature recognizable.

11.	In general, which of the following assures of no ringing in the output?(a) Gaussian Lowpass Filter(b) Ideal Lowpass Filter(c) Butterworth Lowpass Filter(d) All of the mentionedThe question was posed to me during an online exam.Origin of the question is Gaussain Lowpass and Sharpening Frequency Domain Filters topic in section Filtering in Frequency Domain of Digital Image Processing
Answer» Correct CHOICE is (a) Gaussian LOWPASS FILTER The explanation: Using Gaussian Lowpass Filter no ringing is assured, but IDEAL Lowpass Filter and BUTTERWORTH Lowpass Filter of order 2and more produces significant ringing.

12.	If the Gaussian filter is expressed as H(u, v) = e^(-D^2 (u,v)/2D 0^2),where D(u, v) is the distance from point(u, v), D0is the distance defining cutoff frequency, then for what value of D(u, v) the filter is down to 0.607 of its maximum value?(a) D(u, v) = D0(b) D(u, v) = D0^2(c) D(u, v) = D0^3(d) D(u, v) = 0The question was asked in an interview for internship.The doubt is from Gaussain Lowpass and Sharpening Frequency Domain Filters topic in chapter Filtering in Frequency Domain of Digital Image Processing
Answer» The correct CHOICE is (a) D(u, v) = D0 To explain: For the given GAUSSIAN filter of 2-D IMAGE, the VALUE D(u, v) = D0gives the filter a down to 0.607 of its MAXIMUM value.