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Automatic Thresholding

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26 Mar 2003 (Updated )

Provides automatic thresholding based on the ISODATA method.

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Description

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.

Reference :T.W. Ridler, S. Calvard, Picture thresholding using an iterative selection method, IEEE Trans. System, Man and Cybernetics, SMC-8 (1978) 630-632.

Acknowledgements

This file inspired Automatic Thresholding, Automatic Thresholding, and Ridler Calvard Image Thresholding.

Required Products Image Processing Toolbox
MATLAB release MATLAB 6.5 (R13)
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Comments and Ratings (19)
03 Mar 2013 homym Hoi  
03 Mar 2013 homym Hoi

It's what I need!

10 Oct 2012 sheema mathias


Hi!
The code has been useful so far,but when i use certain grayscale images I get the following error:
??? Undefined function or variable "Threshold".

Error in ==> isodata at 68
level = (Threshold - 1) / (N(end) - 1);

do you know of a way i can resolve this?

09 Mar 2012 shan

Thanks for your code its really very good

07 Mar 2010 Upasna

Hi!
The code has been useful so far,but when i use certain rgb images I get the following error:
??? Undefined function or variable "Threshold".

Error in ==> isodata at 68
level = (Threshold - 1) / (N(end) - 1);

do you know of a way i can resolve this? Many thanks.

27 May 2008 Usman Ahmad  
15 Jan 2008 lee lang chua

Hi,ur code is useful to me.but, I also need the PCA source code to extract the bright region from the blood vessel in the retinal image. can anyone send it to me if found? thank you.

22 Jun 2006 JINGFU JIN  
13 May 2006 Ali Tavallaei

Thank you . God bless u

03 Mar 2006 mahendran mariappan  
22 Feb 2006 Vikas Humbe

It is nice

21 Nov 2005 fan zhang

It has a bug!
When the program run to "while abs(T(i)-T(i-1))>=1" for the first time: if T(i)-T(i-1)=0,then the Var "Threshold" can't get a value!
we should set a default value for Var "Threshold" before 56#"while...."

02 Mar 2005 FABIAN ROMERO

it´s true, is better than graythresh

09 Feb 2005 sagar jambhorkar

it is useful

13 Jan 2005 Senes Yin

It's what I need!

15 Sep 2004 Raghavan Gopalakrishnan

better than graythresh

12 Jun 2004 Toni Amengual

I need information about ISODATA for studies

25 Jun 2003 rojas julio

good

01 Apr 2003 george cranberry

fast implementation, faster than graythresh but yiled comparable results. works like a charm!

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