how to find center point coordinates of circles in an image file

Dear friends

I need to find out the center point coordinates of circles in an image file. I read that hough transformation method can find the circles but my attempts to use this function was unsuccessful.

Here is a sample image file which has four white circular shape on it.

I appreciate very much for your help.

Regards

Suleyman

Answer 1

[Anand]

You can use imfindcircles to find the circles. The function returns circle centers and radii. If the circles can't be found using default parameters, look at this post by Steve Eddins and Spandan Tiwari for some insight into adjusting parameters:

http://blogs.mathworks.com/steve/2012/09/04/detecting-circular-objects-in-images/

A first pass:

%read image
im = imread('http://kimyamuhendisi.com/images/pipe.jpg');

%call imfindcircles
[c,r] = imfindcircles(im,[10,20]);

%display detected circles
imshow(im);viscircles(c,r);

[Suleyman Deveci]

Thank you so much. This is just what I want.

[Suleyman Deveci]

Hi Anand,

How can I apply this in a for loop? I have 100 images with names as image1.jpg, image2.jpg, ....image99.jpg.

How can I read and use imfindcircles function for all images I have in sequence?

Thank you for your reply in advance?

Suleyman

[Image Analyst]

Code examples are in the FAQ:

http://matlab.wikia.com/wiki/FAQ#How_can_I_process_a_sequence_of_files.3F

[Suleyman Deveci]

Thanks again.

Answer 2

[Image Analyst]

Alternatively you could threshold, and call regionprops() asking for the EquivDiameter and Centroid, as shown in my Image Segmentation Tutorial.