T f

The number of failures that can be tolerated. The running time must be finite, regardless of whether the correct results are obtained.

T r

The ratio threshold of co-circle pixels. It is used to replace the global threshold

T g

The number of pixels at the edge of circle, T g = 2 π r T r , r is the radius of possible circle.

T a

The threshold of distance. The distance between any two agent pixels of the possible circle should be larger than T a .

T d

The distance threshold for co-circle. It means that the fourth selected pixel is closed to the possible circle, which is determined by the other three pixels.

T c

The number of circles that we want to detect in image.

T r L

The minimal radius that the possible circle should fit.

T r U

The maximal radius that the possible circle should fit.