An effective non-HT circle detection for centers and radii

We present a non-HT circle detection algorithm applied to search the centers and radii of circular or partially circular components present in the image. The line coincident with the gradient vector of each edge point and passing through the corresponding edge point is defined first. Then, for every pixel in the image, the number of the lines passing through this pixel is defined as the energy of the pixel. The feature circle energy (FCE) distribution map of the whole image is therefore obtained and the local maxima are corresponding to the centers of potential circles. For the detection of radius, the gradient magnitudes in assigned region are accumulated and its variation defined as the feature circle radius (FCR) is computed who has maximum when the radius of the region is equal to that of the circle. Synthetic images and natural images are used to test the capability of the proposed method. The experimental results indicate that the presented algorithm has excellent performance for detection of single circle, multiple circles, concentric circles and partial circles, and also good accuracy despite the presence of different noises.