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Subject: Re: HELP!How can I konw a fft2 processed image's frequency value
Date: Mon, 24 Nov 2008 11:43:02 +0000 (UTC)
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"liu " <yacheeliu@yahoo.com.cn> wrote in message <gge3bc$sbm$1@fred.mathworks.com>...
> I want to use band-pass filter to wipe off some regular background pettern from a image after FFT and fftshift processing.My problem is how can I know the frequency value of th regular pattern or other frequency of the image in Matlab.

make an image of the pattern alone, and do its FFT. 

However, removing a pattern from an image is not so easy: the frequencies that constitute your pattern will probably overlap with the frequencies of the image itself. Therefore, if you simply remove all the frequencies constituting the pattern, you'll also alter the image.

Secondarily, if your pattern is not a sine, it will have more than one frequency, and most likely an infinite number of frequencies.