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what does it mean "windowing and truncation in fequency domain "

Asked by Zuhaib on 12 Dec 2012

how truncation is performed on image using different windows and does that window size depend on original image

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Zuhaib

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2 Answers

Answer by Image Analyst on 13 Dec 2012
Accepted answer

Basically you multiply the FFT (spectrum, Fourier Domain) by something that zeros out or attenuates higher frequencies. This "truncates" the spectrum. You choose the window size. It does not depend on the original image size, except that if the width of the truncating window is too huge (wider than the spectrum), you wouldn't be truncating anything. So in a very indirect way it depends on the image size (because hte spectrum size depends on the image size and thus the largest truncating window depends on the image size), but not really directly.

3 Comments

Zuhaib on 13 Dec 2012

if you do not mind then suggest me window size for 515*512 image and tell me how to generate that because i am at beginner level of image processing in Matlab

Image Analyst on 13 Dec 2012

I suggest you try a variety of windows such as 32 by 64, 8 by 128, 16 by 16, and observe in each case how it affects the image, and try to understand why.

Zuhaib on 18 May 2013

thank you for your assistance

Image Analyst
Answer by Arthur on 12 Dec 2012

I used some thing like your question when i worked with Fourier transform. And the analysis could be on the frequecy domain (frequency spectrum)

Or a window of a cicle is used to generate the RMS value of a wave of many of cicles. step by step. (its a way of windowing).

I did not sure if it is your question.

4 Comments

Image Analyst on 13 Dec 2012

But it doesn't. You can choose whatever window size you want.

Arthur on 13 Dec 2012

ok! I think it does not need, but I think it would facilitate the work if it were integer multiple of the main image. As the friend suggested

Image Analyst on 13 Dec 2012

Nothing will be facilitated. Integer multiple (which of course won't have any effect whatsoever) or integer divisor (which is what I think you meant) - none of those are any better or easier than picking some arbitrary window width. It just doesn't matter.

Arthur

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