# how to detect center of a blurry circle with opencv

I have got the following image:

There are curvs on the picture. i would like to find center of the circles containing curves.

• are all the curves concentric? is the spacing between them variable? – endolith Jul 19 '12 at 19:14
• yes, they are concentric. and no spacing is constant. – JingKe Jul 19 '12 at 20:23

You'll need to improve the contrast of the image first, then filter it strongly to remove the noise. since the circles are 'thick' (blurry), you can filter quite a bit without destroying the circles structure.

I would then apply some edge detection algorithm to get a binary edge image that can be processed by the Circular Hough Transform.

I get the following edge image from your image:

Using the following MATLAB commands:

 % x is the input grayscale image. First we adaptively improve the contrast over the image