Contrast Limited Adaptive Histogram Equalization (CLAHE)

Best to read the reference in "Graphics Gems IV", Academic Press, 1994 pages 474-485

Description

This is an image contrast enhancement algorithm that overcomes limitations in standard histogram equalization (HE). The two primary features is adaptive HE (AHE), which divides the images into regions and performs local HE, and the contrast limited AHE (CLAHE), which reduces noise by partially reducing the local HE. Bilinear interpolation is used to avoid visibility of region boundaries.

  "Contrast Limited Adaptive Histogram Equalization"
  by Karel Zuiderveld, [e-mail]
  in "Graphics Gems IV", Academic Press, 1994

Ported by Leslie Smith

• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 7.4 (R2007a)

[Steve Eddins]

You might want to take a look at adapthisteq, which is in the Image Processing Toolbox. This function also implements CLAHE. See:

http://www.mathworks.com/access/helpdesk/help/toolbox/images/adapthisteq.html

[Leslie Smith]

Thanks for the reference. I had looked for and did not find the Matlab CLAHE and was surprised when I thought it did not exist.
Leslie

[Idillus]

 

[Alireza Saberi]

Thank you much, I really was in need to this codes

[Freyssineta]

hey guys.. I got error like this
"Error in ==> runCLAHE at 55
Bin= 1 + LUT(round(Image));"

Do you know the solution?
please help me. I need it

[Leslie Smith]

I suggest you use adapthisteq in the Image processing toolbox because Matlab's routine is more robust.
Although you don't say what the error is, my guess is that it is "index out of bounds" for the look up table LUT. If I remember correctly, runCLAHE needs for the dimensions of the image to be even to work properly. Again, you are likely better off to use adapthisteq.

[Freyssineta]

When i execute runCLAHE.m the error is "Subscript indices must either be real positive integers or logicals"

yup i know about adapthistheq function in matlab. But i did'nt allowed to use that function with my lecturer so i must make clahe code manually.
What should i do?

[Leslie Smith]

The "Subscript indices must either be real positive integers or logicals" is basically that the index is out of bounds.

Obviously you are taking a class where the assignment is to create the CLAHE code. IMO, that is what you should do because the goal of a class is the learning, not the grade.

[Rado]

Excuse me, this may be a stupid question, but can you tell me how to use this function?

I tried to define the variable "Image" to be the path of the image I want to process. Then I removed the comment symbols in front of:
% [XRes,YRes]=size(Image);
% CEimage = Image;
in "runCLAHE.m".

I typed the command:
J=runCLAHE(Image);

The error I got was:
?? Input argument "Cliplimit" is undefined.

Error in ==> runCLAHE at 34
if Cliplimit == 1

Can you help me with that?

Again, sorry for the stupid question and thanks in advance!

[Leslie Smith]

The full argument list is
runCLAHE(Image,XRes,YRes,Min,Max,NrX,NrY,NrBins,Cliplimit,modHist)
The comments in the beginning of the function describe the arguments.
Once again I will suggest you use adapthisteq in the Image processing toolbox because Matlab's routine is more robust.

[LIAO xj]

quite useful! thanks a lot!