### Highlights from Automatic Thresholding

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# Automatic Thresholding

### Gauthier Fleutot (view profile)

01 Jul 2004 (Updated )

How to find a good default threshold value?

File Information
Description

Dhanesh Ramachandram posted on same algorithm, march 2003.

This iterative technique for choosing a threshold was developed by Ridler and Calvard . The histogram is initially segmented into two parts using a starting threshold value such as 0 = 2B-1, half the maximum dynamic range.

The sample mean (mf,0) of the gray values associated with the foreground pixels and the sample mean (mb,0) of the gray values associated with the background pixels are computed. A new threshold value 1 is now computed as the average of these two sample means. The process is repeated, based upon the new threshold, until the threshold value does not change any more.
(quote from http://www.ph.tn.tudelft.nl/Courses/FIP/frames/fip-Segmenta.html)

New feature from the m-file of Dhanesh Ramachandram:
- one does not have to rescale one's image to a uint array. This algorithm works for negative intensities, for example.

Run:
vImage = Image(:);
[n xout]=hist(vImage, <nb_of_bins>);
threshold = isodata(n, xout)

You get a (hopefully relevant) threshold for your image.

Acknowledgements

Automatic Thresholding inspired this file.

This file inspired Ridler Calvard Image Thresholding.

MATLAB release MATLAB 6.5 (R13)
26 Jul 2012 Christina

### Christina (view profile)

20 Oct 2009 Atta-Ul Ghaffar

### Atta-Ul Ghaffar (view profile)

Not too bad. I found the following error on line 27:
mat = sum(count(T_i:end) .* intensity(T_i:end) ) ./ sum(count(T_i:end));

The calculations should run from, T_i + 1 : end

23 Feb 2009 neftirini isabel

### neftirini isabel (view profile)

what's <nb_of_bins>); ?

Comment only
21 Jul 2008 hanno walter

perfect for me

10 Mar 2008 Farry anto