Detect circles with various radii in grayscale image via Hough Transform

Detect circular shapes in a grayscale image. Resolve their center positions and radii.

Description

Circular Hough transform based on the gradient field of an image.
1. Operates on grayscale images, NOT B/W bitmaps.
2. NO loops in the implementation of Circular Hough transform, which means faster operation but at the same time larger memory consumption.
3. Detection of radii works for concentric circles as well.

• Acknowledgements: This submission has inspired the following:; Coin Segmentation
• Required Products: Image Processing Toolbox
• MATLAB release: MATLAB 7.0.4 (R14SP2)
• Other Files: CircularHough_Grd.m, ; DrawCircle.m, ; Frame_0_0022_portion.jpg, ; license.txt, ; TestImg_CHT_a2.bmp, ; TestImg_CHT_a3.bmp, ; TestImg_CHT_b3.bmp, ; TestImg_CHT_c3.bmp

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[Gijs H]

Excellent work, well documented, easy to use.
Thanks!

[Iftach Nachman]

Excellent! Works amazingly well in detecting yeast cells in microscopy images.

[ali volkan]

Perfect

[Nurettin Senyer]

Thank you for EXCELLENT work. Surely, well document and easy to use.

[veli birol]

clearly and fast.

[Dany Simard]

Clear and efficient

[Sander L]

This code can be of great help in my project on pollen recognition in microscopic images. Thanks!

There is one problem however. For some(!) images I get the error message:
-----------------------------
??? Attempted to access SgnCv_LMPos(0); index must be a positive integer or logical.

Error in ==> CircularHough_Grd at 630
    cirrad(k) = SgnCv_LMPos(end);
-----------------------------
Can anyone help?

[Erinc D]

Thanks for sharing this file, it helps a lot!
However, I'm having the same strange problem too (see below). I understand that this is an issue about radius range selection, but I cannot predict which values would make it work.

[Tao Peng]

Hi, Sander and Erinc: The problem you have experienced is a bug in the code and it has been fixed (at least I think so :)). The revised version (March 7, 2007) will soon be posted by Matlab Central. Thank you for pointing out the problem.
Although I have requested that all user comments to be forwarded to my email, a couple of messages here seemed to have slipped. Therefore I would appreciate everyone who has questions about the code does send me emails. I can't guarantee a timely and satisfactory response but I'll do my best.

[Sander L]

I've solved it by changing the code around line 650 into this:

% Save the detected radii
if (length(SgnCv_LMPos) ~= 0)
    cirrad(k) = SgnCv_LMPos(end);
    for i_radii = (length(SgnCv_LMPos) - 1) : -1 : 1,
        circen = [ circen; circen(k,:) ];
        cirrad = [ cirrad; SgnCv_LMPos(i_radii) ];
    end
end

[Paul Premakumar]

Kudos to you!Your program is amazing. Your examples were great.
Thanks!

[hani ali]

good article

[Dr Samir badawy]

it straightforward. easy to follow and operate. not tested the programs on the MATLAB yet.

[Robert Keck]

Note that this also requires the Signal Processing Toolbox since it uses the filtfilt function.

[Martin Ohmes]

Excellent code with great documentation - this code saved my butt. It is a little memory intensive but with a few tweaks I got it working great for some detailed image analysis.

[Slobodan Vrhovac]

This code can be of great help in my project on disk recognition in experiments with granular materials.

[Nat Angarita]

Very good code, robust,...the only downside...it provides the values of the estimated radious as whole integers...could not see where I could change this in the code!

[Joan Wang]

Excellent performance!

[Vinh Nguyen]

 

[Ohil K]

I tried out this code, and I dont know if this problem can be solved. When I run the code on an image that has some straight lines too, all along the edge of the straight line, circles are detected. Is there a way to prevent this? I tried changing the threshold but to no avail.

[Lee Borland]

Hi all. This may seem like a silly question, but how does one run an add on file such as this? I am attempting to detect circles in images. So far, the only code I have in matlab is open/close code to enhance my edges, then blob analysis to detect my circles and finally convex hull code to fill in my circles. So I now have a BW image containing 4 white circles, very much like the images in the examples.

Can someone advise as to how i now implement this file for radius calculations? I attempted to copy and paste but got the error: Error: Function definitions are not permitted at the prompt or in scripts.

Obviously missing something silly here, can anyone help??

[Roxy]

I have been getting an error on one of your files when i try running it, there is no function name filtfilt.

[Gregory Van der Steen]

Great work, excellent performance and good results. The algorithm is perfectly customizable by its number of parameters. Thanks, this was the important part of a solution for a problem of weeks.

[Ken Jarman]

Excellent code and helpful comments on test cases. If you don't have IPToolbox or SPToolbox, you can still use this if you create or pick up a third-party version of bwlabel.m (labels blobs of dark/light pixels) and filtfilt.m (fwd/bkwd filter).

[Pavithra]

thanks for sharing

[Samuele Lilliu]