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 file inspired Coin Segmentation.

• Required Products: Image Processing Toolbox; Signal Processing Toolbox
• MATLAB release: MATLAB 7.0.4 (R14SP2)

[math works gowroju]

???Attempted to access SgnCv_LMPos(0); index must be a
positive integer or logical.
what to do with this error?

[Yashasvi Purwar]

Why I am getting zero radii despite of providing radii range greater than zero. Thanks

[Shubham]

 

[Amalia adiba]

Dear Mr Taopeng

would you please give me a reason, why while i compile from any example on your program, i got this error

??? Maximum recursion limit of 500 reached. Use set(0,'RecursionLimit',N)
to change the limit. Be aware that exceeding your available stack space can
crash MATLAB and/or your computer.

Error in ==> imbmpinfo>decodeCompression

I'm using matlab 7.8 (2009a)
there's no problem while i try to call

rawimg = imread('TestImg_CHT_a3.bmp');

Thank you for yor reply

[Amalia adiba]

 

[Daniel Delgado]

Hello, I really need your help. I'm trying to detect the circle center of those red ball images but I can't find the correct parameters to make CircularHough_Grd to work. Thank you in advance, it's kinda urgent. It used to work perfectly on 160x120 images but now that those are 640x480 it fails.

Here is my code:

x = 90;

%% Read images
%images[];
for n=1:(numel(x)/3)
images{n} = imread(sprintf('%d.jpg',n));
end

Temp = imfinfo('1.jpg');
width =Temp.Width;
height = Temp.Height;

%% Detect circles centers
tic;
for n=1:length(images)
img = images{n};
img2 = imadjust(img, [0 .7], [0 .5]);
%img = imresize(img, 2);
red = img2(:,:,1);
% red = img(:,:,1);
%red = adapthisteq(red);
fltr4img = [1 1 1 1 1; 1 2 2 2 1; 1 2 4 2 1; 1 2 2 2 1; 1 1 1 1 1];
% fltr4img = [1 1 1 1 1; 1 4 4 4 1; 1 4 12 4 1; 1 4 4 4 1; 1 1 1 1 1];
% fltr4img = [1 1 1 1 1; 1 4 8 4 1; 1 4 8 4 1; 1 4 8 4 1; 1 1 1 1 1];
% fltr4img = fltr4img / sum(fltr4img(:));
% imgfltrd = filter2( fltr4img , red );
% imgfltrd = filter2( fltr4img , img2(:,:,1) );
imgfltrd = filter2( fltr4img , red );
% imgfltrd = red;

%tic;
% [accum, circen, cirrad] = CircularHough_Grd(imgfltrd, [15 80], 8, 10);
% [accum, circen, cirrad] = CircularHough_Grd(imgfltrd, [0 26], 3, 4, 1);
% [accum, circen, cirrad] = CircularHough_Grd(red, [11 50], 20, 13, 1);
[accum, circen, cirrad] = CircularHough_Grd(imgfltrd, [90 120], 50, 5, 1);
%toc

if(length(circen)==2)
%circenaccum {n} = circen(1,:)';
circenaccum{n} = [circen(1,1);circen(1,2)];
%circenaccum{n} = [(circen(1,1)-(width/2));(circen(1,2))-(height/2)];
else
circenaccum{n} = [0;0];
end

% if any(cirrad <= 0)
% inds = find(cirrad>0);
% cirrad = cirrad(inds);
% circen = circen(inds,:);
% end

%imshow(img);
figure(1); imagesc(accum); axis image;
title('Accumulation Array from Circular Hough Transform');
% figure(2); imagesc(img2); colormap('gray'); axis image;
% figure(2); imagesc(img); colormap('gray'); axis image;
figure(2); imagesc(imgfltrd); colormap('gray'); axis image;
% figure(9); surf(accum, 'EdgeColor', 'none'); axis ij;
% title('3-D View of the Accumulation Array');
hold on;
plot(circen(:,1), circen(:,2), 'r+');
% for ii = 1 : size(circen, 1)
% rectangle('Position',[circen(ii,1) - cirrad(ii), circen(ii,2) - cirrad(ii), 2*cirrad(ii), 2*cirrad(ii)],...
% 'Curvature', [1,1], 'edgecolor', 'b', 'linewidth', 1.5);
% end
for k = 1 : size(circen, 1),
DrawCircle(circen(k,1), circen(k,2), cirrad(k), 32, 'b-');
end
hold off;
title(['Raw Image with Circles Detected ', ...
'(center positions and radii marked)']);
% pause;
end
toc

%% Draw center points
figure
circenaccummat = cell2mat(circenaccum);
scatter(circenaccummat(1,:),circenaccummat(2,:))
% plot(circenaccummat(1,:), circenaccummat(2,:),'*b');
axis ij;

[Fer]

 

[ketan patil]

I didn't understand following part in code
.
rr_4linaccum = double( prm_r_range ); %prm_r_range contain all the sort values of radius in ascending order
linaccum_dr = [ (-rr_4linaccum(2) + 0.5) : -rr_4linaccum(1) , ...
(rr_4linaccum(1) + 0.5) : rr_4linaccum(2) ];

lin2accum_aJ = floor( ...
double(grdx(grdmasklin)./grdmag(grdmasklin)) * linaccum_dr + ...
repmat( double(grdmask_IdxJ)+0.5 , [1,length(linaccum_dr)] ) ...
);
lin2accum_aI = floor( ...
double(grdy(grdmasklin)./grdmag(grdmasklin)) * linaccum_dr + ...
repmat( double(grdmask_IdxI)+0.5 , [1,length(linaccum_dr)] ) ...
);
plese tell me

[Vilém Rechtacek]

Hello,

function CircularHough_Grd works very well for images, but I need to process video stream (for example from web camera). I want to detect eyes in video stream. I want to use CircularHough Tansform for detection of iris, becouse iris have circular shape. I assume, that the face fills the entire scanned image space, so I do not need to detect face.

Can anyone help me? When you send me the complete code, it would be best for me.

Thank you.
Vilem Rechtacek

[Vince]

I'm fairly new to image processing, but I can follow your code halfway decent.

However, I am capturing an image from a webcam, and cant seem to get the function to work. What format should the image be in? I've tried to save it as several formats, but either get a lime green image as the result, or an error saying the image must be 2-dimensional. Any suggestions?

[Serena]

 

[Ralvin Kumar]

For my application I am using this CircularHough_Grd function to detect COLORED circles.It works fine for red,green,blue,however, it does not get yellow circles or lighter circles.
Here is the image i'am working on:
http://i.imgur.com/OOrmZ.png

And this is what i get with my current codes:
http://i.imgur.com/tP1BY.jpg

My code is :

rgb = imread('capture4.bmp');
rawimg = rgb2gray(rgb);

% rawimg = rgb(:,:,1);

fltr4img = [1 1 1 1 1; 1 2 2 2 1; 1 2 4 2 1; 1 2 2 2 1; 1 1 1 1 1];
fltr4img = fltr4img / sum(fltr4img(:));
imgfltrd = filter2( fltr4img , rawimg);
tic;
[accum, circen, cirrad] = CircularHough_Grd(imgfltrd, [2 20], 0, 3, 0.1);
toc;
figure(1); imagesc(accum); axis image;

figure(2); imagesc(rgb); colormap('gray'); axis image;
hold on;

plot(circen(:,1), circen(:,2), 'r+');axis image;
impixelinfo;
for k = 1 : size(circen, 1),
DrawCircle(circen(k,1), circen(k,2), cirrad(k), 32, 'r-');
end
hold off;
title(['Raw Image with Circles Detected ', ...
'(center positions and radii marked)']);

[Sarah]

 

[Paulo]

nice! thanks!

[Kfir]

For some reason, I can't get this to work. I can get the 'accum' matrix and can visually find the local maxima, but the 'circen' and 'cirrad' remain empty.
Any suggestions as to what I should do or which parameters I need to experiment with?
(and I get an error message many times:
"??? Undefined function or method 'filtfilt' for input arguments of type 'double'.

Error in ==> CircularHough_Grd at 606
SgnCv = filtfilt( fltr4SgnCv , [1] , SgnCv );"

[Joseph Corcoran]

For my application I am trying to identify circles that have different radii but similar (but not the same) centre points- They are sufficiently different that I would of thought that it would be possible to seperate them.
Anyone know of a way that I can differentiate the two circles?

[Julie]

I keep getting fewer circles when I increase the radius range
example
range =[1 30] # of circles=10
range =[1 50] # of circles=2

I am changing nothing else, is this a bug or am I doing something wrong?

[Karen ortega]

help error :S

[Valentin Romanov]

same problem with Angelo too =((
please if someone knows how avid this - help!

[scholar fathi]

excellent job!!
Thanks a lot!!

[White Apple]

same problem with Angelo. What does the error message means?

[Nagaraju Annamdevula]

 

[Yassine]

Good work! Thanks a lot!

[Pascal]

this is great work.

However, circle detection has been investigated to perfusion. Ellipse detection is crucial, especially ellipses oriented at specific angles.....

[Brett Shoelson]

PLEASE NOTE: As written, this code requires the Signal Processing Toolbox in addition to the Image Processing Toolbox noted as a requirement above. (There's a single call to FILTFILT, which one may be able to replace with a couple calls to MATLAB's FILTER function.)

[Angelo]

Hi! why do i get this error message?

??? Maximum recursion limit of 500
reached. Use set(0,'RecursionLimit',N)
to change the limit. Be aware that
exceeding your available stack space
can
crash MATLAB and/or your computer.

Error in ==>
imbmpinfo>decodeCompression

[bass sawet]

Excellent code!! THX isn t enough

[Fredrik]

Very well written code with extremely good examples and very well commented. Can't thank you enough!

[Fredrik]

 

[Truc Phan]

Excellent and easy-to-use code with very useful documentation.
Works well in detecting small circles, but less robust for larger ones.
Thanks a lot for the great work.

[Samuele Lilliu]

 

[Pavithra]

thanks for sharing

[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).

[Artesis]

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.

[Roxy]

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

[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??

[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.

[Vinh Nguyen]

 

[Joan Wang]

Excellent performance!

[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!

[Slobodan Vrhovac]

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

[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.

[Robert Keck]

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

[Dr Samir badawy]

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

[hani ali]

good article

[Paul Premakumar]

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

[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

[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.

[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.

[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?

[Dany Simard]

Clear and efficient

[veli birol]

clearly and fast.

[Nurettin Senyer]

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

[ali volkan]

Perfect

[Iftach Nachman]

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

[Gijs H]

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

[e d]