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Reply-To: "Nasser Abbasi" <nma@12000.org>
From: "Nasser Abbasi" <nma@12000.org>
Newsgroups: comp.soft-sys.matlab
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Subject: Re: how to transform the power spectra image into spectrum diagram?
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Date: Thu, 9 Apr 2009 05:08:33 -0700
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<islinaismail@gmail.com> wrote in message 
news:12b90af4-28c5-42f5-bf54-4234749f1364@r28g2000vbp.googlegroups.com...
>I want to ask...is it possible to differentiate 2 different images by
> using the fft2 function in matlab?
> If i'm not mistaken, fft2 converts the image into cos and sin
> function..Is it possible to differentiate the images (power spectrum
> image) by looking only at its phase and magnitude diagram?thanks..

I think you are mixing terms a little here.

PSD is not the spectrum. PSD has no phase information in it, only magnitude 
information of the spectrum. PSD=|X(w)|^2.

Therefore, different images can give the same PSD, it is not unique.

You need both phase and magnitude.  If you are looking at spectrum only, 
then looking at the magnitude and phase of each image spectrum, you can tell 
if these are from same or different image if both magnitude *and* phase data 
is exactly the same or not.

--Nasser