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Image segmentation using Otsu thresholding


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Image segmentation using Otsu thresholding



29 Jan 2010 (Updated )

OTSU(I,N) segments the image I into N classes by means of Otsu's N-thresholding method.

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IDX = OTSU(I,N) segments the image I into N classes by means of Otsu's N-thresholding method. OTSU returns an array IDX containing the cluster indices (from 1 to N) of each point.
IDX = OTSU(I) uses two classes (N=2, default value).
[IDX,sep] = OTSU(I,N) also returns the value (sep) of the separability criterion within the range [0 1]. Zero is obtained only with data having less than N values, whereas one (optimal value) is obtained only with N-valued arrays.

If I is an RGB image, a Karhunen-Loeve transform is first performed on the three R,G,B channels. The segmentation is then carried out on the image component that contains most of the energy.
    load clown
    X = ind2gray(X,map);
    for n = 2:4
      IDX = otsu(X,n);
      imagesc(IDX), axis image off
      title(['n = ' int2str(n)],'FontWeight','bold')

See also:

MATLAB release MATLAB 7.5 (R2007b)
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Comments and Ratings (8)
25 Apr 2013 Venkat  
09 Jul 2012 Jing

Thanks a lot for the code!
I just have a question: in the n=2 case, what's the meaning for the following code? I tried to derive the equation, but could not make it. Would you please explain a bit? Thanks!!

sigma2B =...

21 Jan 2012 Jamuna Jayashri Mahalingam

I am geting this error...How do I correct it?

Undefined function or method 'otsu' for input arguments of type 'uint8'.

11 Feb 2011 Samuele

works smoothly...thx ;)

13 Oct 2010 Matteo Niccoli

It has worked for me very nicely. I like to run it in a while loop that breaks when sep starts decreasing.

10 Jul 2010 Dalal

i am trying to segment the image of signature
is it possible to apply the same code ?
thank you

28 Apr 2010 Fu  
11 Mar 2010 Lukas Lansky

Works nice!

31 Jan 2010

New screenshot.

28 Feb 2010

RGB images are now analyzed in the gray, R, G and B scales.

04 Mar 2010

The segmentation for RGB image has been improved: a KLT is performed and we keep the component of highest energy.

10 Mar 2010

Minor modifications

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