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From: "Yang Zhang" <zhyang99@hotmail.com>
Newsgroups: comp.soft-sys.matlab
Subject: Re: How to find similar images
Date: Wed, 8 Aug 2007 22:44:24 +0000 (UTC)
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"Yair Altman" <altmanyDEL@gmailDEL.comDEL> wrote in message
<f9dggq$lu8$1@fred.mathworks.com>...
> I have a large set of color images. I wish to find a
> characteristic number for each of them, so closer numbers
> would represent "similar" images (in very loose terms). I'd
> like the characteristic to be tolerant to cropping &
> resizing and if possible also to rotation, flipping &
> saturation. If possible, I'd also like it to be computed
> quickly (my set is very large).
> 
> The ultimate aim is to winnow down the large set to a much
> smaller subset of potential matching images, that would then
> be inspected manually.
> 
> Some simple functions that I thought of were the grayscale
> rms/mode/std/kurtosis/skewness. Could anyone please comment
> on which of these functions (or any other) would be best for
> my needs?
> 
> (I'm not an imaging expert nor have the Image Processing
> Toolbox...)
> 
> Thanks in advance,
> Yair


Hi Yair,

Did you know PCA before? It may help you in this case. 
Help: princomp

Also, k-means may be useful after you use PCA to reduce your
matrices size.

HTH,
Yang