<p>You are asking for an answer to a very hard problem. The hough algorithm is not a toy solution, but it is not appropriate for all machine visions circle detection situations. Human eyes are very good at such thing (if a bit imprecise). You basically need to know a lot more about your data to approach a robust solution.</p>

<p>Take a look at <a href="https://stackoverflow.com/questions/9860667/writing-robust-color-and-size-invariant-circle-detection-with-opencv-based-on">this dicussion about Hough Circle detection</a> as well as this paper <a href="http://www.egr.msu.edu/classes/ece480/capstone/fall10/group03/ece480_dt3_application_note_dembelef.pdf" rel="nofollow noreferrer">Hough Circle Transform</a> for a deeper understanding of the limitations</p>

<p>You might also want to review this paper on the <a href="http://arxiv.org/ftp/arxiv/papers/1106/1106.0962.pdf" rel="nofollow noreferrer">ant system</a> for ideas on a different approach.</p>

<p>You also might want to read up on <a href="http://homepages.inf.ed.ac.uk/rbf/HIPR2/thin.htm" rel="nofollow noreferrer">Morpological thinning</a> as a possible pre-preprocessing step before Houghton</p>

<p>Best of luck</p>
Get diameter of circle in bitmap
<p>My problem is following. I need precisely measure diameter of circles in bitmap.
I have Bitmap with several circles. Some of them are concentric. I need values of their diameters.
I tried OpenCV and EmguCV and their method HoughCircles. But this method find circles on the places where is are no circles (I tried a lot of combinations of input parameters). Ad if it finds them there is no case, when it found exatly same circle as in the bitmap. Their centers and diameters are different then circles on the original picture. So this method is only for some kind of game. Not for my purpose(precise measuring for industry). </p>

<p>Do you know some way or algorithm how to do it? (I prefer C#, but if it will be in pseudocode or different langueage, I will rewrite it)</p>

<p>Thanks in advance.</p>