Here are the HoughCircles parameters and default arguments:
void cv::HoughCircles(
- InputArray image, //8-bit,
single-channel, grayscale input
image.
- OutputArray circles, // Output vector
of found circles. Each vector is
encoded as a 3-element floating-point
vector (x,y,radius)
- int method, //Detection method, see
cv::HoughModes. Currently, the only
implemented method is HOUGH_GRADIENT
- double dp, //Inverse ratio of the
accumulator resolution to the image
resolution. For example, if dp=1 ,
the accumulator has the same
resolution as the input image. If dp=2 , the accumulator has half as big width and height.
- double minDist, //Minimum distance
between the centers of the detected
circles. If the parameter is too
small, multiple neighbor circles may
be falsely detected in addition to a
true one. If it is too large, some
circles may be missed.
- double param1 = 100, // First
method-specific parameter. In case of
CV_HOUGH_GRADIENT , it is the higher
threshold of the two passed to the
Canny edge detector (the lower one is
twice smaller).
- double param2 = 100, //Second
method-specific parameter. In case of
CV_HOUGH_GRADIENT , it is the
accumulator threshold for the circle
centers at the detection stage. The
smaller it is, the more false circles
may be detected. Circles,
corresponding to the larger
accumulator values, will be returned
first.
- int minRadius = 0, //Minimum circle
radius.
- int maxRadius = 0 //Maximum circle
radius.
)
Note:
Usually the function detects the centers of circles well. However, it may fail to find correct radii. You can assist to the function by specifying the radius range ( minRadius and maxRadius ) if you know it. Or, you may ignore the returned radius, use only the center, and find the correct radius using an additional procedure.
Also, here is a tutorial with a sample code and explination
