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Subject: Re: HELP!How can I konw a fft2 processed image's frequency value
Date: Mon, 24 Nov 2008 13:32:01 +0000 (UTC)
Organization: Helbling Technik Bern AG
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"liu " <yacheeliu@yahoo.com.cn> wrote in message <gge61q$s1o$1@fred.mathworks.com>...
> "Gavrilo Bozovic" <gavrilo.bozovic@helbling.ch> wrote in message <gge406$646$1@fred.mathworks.com>...
> > 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.
> 
> If it is regular it will have many sub-frequencis ,can I wipe off these sub-frequencis?

It depends. If it's a sine, it will have one frequency. You can then proceed to delete completely this frequency from your global image, but this is likely to alter your image. It's as if you hade a blue stain on a picture, and decided to remove it by removing all the blue: you'd alter the picture.

Then, if it is not a sine, if it is a grid, for instance, the pattern will have infinite frequency components. At this point, you can also try to remove all these components, but you'll also alter your image.

Basically, it's more complicated than this....

what kind of pattern do you have? is it simply a grid?