Method CornerSubPix

adjusts the corner locations with sub-pixel accuracy to maximize the certain cornerness criteria

public static Point2f[] CornerSubPix(InputArray image, IEnumerable<Point2f> inputCorners, Size winSize, Size zeroZone, TermCriteria criteria)

image InputArray: Input image.
inputCorners IEnumerable<Point2f>: Initial coordinates of the input corners and refined coordinates provided for output.
winSize Size: Half of the side length of the search window.
zeroZone Size: Half of the size of the dead region in the middle of the search zone over which the summation in the formula below is not done. It is used sometimes to avoid possible singularities of the autocorrelation matrix. The value of (-1,-1) indicates that there is no such a size.
criteria TermCriteria: Criteria for termination of the iterative process of corner refinement. That is, the process of corner position refinement stops either after criteria.maxCount iterations or when the corner position moves by less than criteria.epsilon on some iteration.