Automatic Thresholding

Provides automatic thresholding based on the ISODATA method.

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 submission has inspired the following:; Automatic Thresholding, Automatic Thresholding
• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 6.5 (R13)

[george cranberry]

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

[rojas julio]

good

[Toni Amengual]

I need information about ISODATA for studies

[Raghavan Gopalakrishnan]

better than graythresh

[Senes Yin]

It's what I need!

[sagar jambhorkar]

 it is useful

[FABIAN ROMERO]

it´s true, is better than graythresh

[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...."

[Vikas Humbe]

It is nice

[mahendran mariappan]

 

[Ali Tavallaei]

Thank you . God bless u

[JINGFU JIN]

 

[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.

[Usman Ahmad]

 

[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.

[shan]

Thanks for your code its really very good