Detecting circle in an image

Hi, I would like to know is it possible to detect the circles in the image below using MATLAB's Image Processing Toolbox. The circles are imperfect and the radius are varied. Anyone can help me with this? Thanks in advance.

[Jan]

I've included the picture directly.

Answer 1

[Image Analyst]

I'd probably just sum the image horizontally and vertically to detect the grid locations and then process the inside of each grid location (each "tile") to see if the mean gray level is less than some number. That's what I think would be the simplest approach.

[Natsu]

Sorry for the trouble, but can you show me how to begin doing this with MATLAB? How can I calculate the pixel value of each tile separately?

[Image Analyst]

meanGrayValue = imageArray(row1:row2, col1:col2);

if meanGrayValue < 150

% It has user-written stuff in it

else

% It's just the number alone.

end

Answer 2

[Sean de Wolski]

One of R2012a's not-so-hidden gems!

doc imfindcircles

[Image Analyst]

Brett uploaded an app based on that: http://www.mathworks.com/matlabcentral/fileexchange/34365-findcirclesgui