Comments on: Detecting Circles in an Image

By: nickey

nickey — Sat, 27 Jun 2009 16:18:47 +0000

Hi Brett,

I’ve tested Tao’s program and yours too. They ran successfully. I’ve tried to applied your method above and Tao’s to detect sun features in an image that comes with text. Some of the suns are detected and some are not. Other features in the image were also detected such as the text.

I thought of removing the text so that it doesn’t interfere the program in detecting the circles in the image but not really sure how. Do you have any ideas how to start?

Many thanks!
Nickey

By: Berkan

Berkan — Thu, 04 Jun 2009 15:05:56 +0000

Hi Brett, I have tried Tao’s function, however I get around 25 bogus circles when I run with the default parameters (CircularHough_Grd(img, radrange, grdthres, fltr4LM_R, multirad, fltr4accum)) on the image link below.

Do you reckon it would work for this image: http://img15.imageshack.us/i/f142.png/ ?

If so, which input parameter shall I tweak?

Would be great if you could point me in the right direction.

Sincerely,
berkan

By: suwei

suwei — Thu, 16 Apr 2009 04:13:11 +0000

Thanks a lot.

By: Brett

Brett — Thu, 16 Apr 2009 03:42:00 +0000

Hi Suwei,
Thanks for pointing this out. Actually, FILTFILT is a function in the Signal Processing Toolbox that does zero-phase digital filtering. So Tao’s function should specify that as a pre-req. A workaround — besides buying the Signal Processing Toolbox ;) — would entail tweaking the code to avoid the dependency.

Cheers,
Brett

By: suwei

suwei — Thu, 16 Apr 2009 02:15:31 +0000

It seems that the function that Tao wrote has a bit of a minor problem, there is a function that is called filtfilt that is not defined. what would u recommend to overcome this problem?

By: et

et — Sun, 08 Mar 2009 00:09:54 +0000

Can I somehow use this algorithm to find grapes in image
like this: http://itamarbarkai.110mb.com/files/temp/slika1674-small.jpg ?

I tried playing for a while with the parameters but in vain.
Thanks Itamar

By: Brett

Brett — Tue, 24 Feb 2009 02:51:30 +0000

Lee, I’m afraid I don’t have any better suggestions for you…except that maybe you can try posting your question to the newsgroup for some additional support. Good luck!
Brett

By: Lee

Lee — Sun, 22 Feb 2009 17:23:23 +0000

Thank you for the help Brett. This is now working nicely for me. I have discovered a further issue however upon implementation of some alternative images I have been given. I have a collection of low res SEM images, similar to your example. Circle detection is not working however. I have altered Taos parameters significantly but to no avail. Any ideas?

See below
Original Image:
http://i44.tinypic.com/2liu3×5.jpg
Result: [Somewhat redundant:(]
http://i42.tinypic.com/2ik4i1c.jpg

By: Brett

Brett — Thu, 12 Feb 2009 19:12:47 +0000

Lee, Notice that in my original code, I didn’t use DrawCircle; I used the RECTANGLE command instead. I later modified my code to return handles to each rectangle so I could show you how to modify their BUTTONDOWNFCNs. If you want to use DRAWCIRCLE, you’ll have to modify it so that it returns a vector of handles to the plots it creates, then similary modify the buttondownfcns of those.
Regards,
Brett

By: Lee

Lee — Tue, 10 Feb 2009 21:40:50 +0000

Sorry Brett but im not sure what you mean. I have the following code to date, simply entered in my command window:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

%% Load image
rawimg = imread(’clll40_005.tif’);
rawimg = rawimg(1:884,:);

%% Image binning
st_imgbin = immBinning( uint16(rawimg), [1,1] );
imgshrunk = uint8( st_imgbin.img / 4 );

%% Image smoothing using Gaussian filter
fltr4img = fspecial( ‘gaussian’, 5, 1.2 );
imgfltrd = imfilter( imgshrunk, fltr4img, ‘replicate’ );

%% Detection of circular features by Hough Transform
tic;
[accum, circen, cirrad] = …
CircularHough_Grd_SL( imgfltrd, [10 190], 6, 25, 0.6 );
toc;

%% Results display
figure(1); imagesc(accum); axis image;
title(’Accumulation Array from Circular Hough Transform’);

figure(2); imagesc(imgfltrd); colormap(’gray’); axis image;
hold on;
plot(circen(:,1), circen(:,2), ‘r+’);
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)’]);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Do I convert this into an m-file? and then add SHOWPROS within? Or do I add showpros as a separate m file?

When you say the SHOWPROS code block, is that everything you have added in the comment above?

And how do I go about knowing what to set r as? is r my required circle?

Overall, sorry im so confused. I’ve very little experience in calling functions to date so this seems to be going over my head so far.

Thanks you for any help you can give me.
Lee