Detecting a circle of a specific color (or gray level) with openCV

Is there a way to detect a circle with a specific grey level using openCV? I want to detect a circle that marks out from the others.

Currently, I'm using cvHoughCircles to detect my circles. I know the method returns an array of cvSeq containing the info on each circle (point and radius), but it does not provide any color i开发者_如何学编程nformation.

Thank you

You should first isolate the colour you want, and then do a houghcircles on that image.

Say you want to find green circles from a bunch of green, red and blue circles. Its simple in this case, just threshold the green channel. You'll get only the green circle in the thresholded image. Do a sobel/canny on it and execute houghcircles.