private void approximation(int counter) {
        MatOfPoint2f approx = new MatOfPoint2f();
        MatOfPoint2f approxCurve = new MatOfPoint2f();
        approxContours = hullmop;
        for (int i = 0; i < counter; i++) {
            hullmop.get(i).convertTo(approx, CvType.CV_32FC2);
            double approxDistance = Imgproc.arcLength(approx, true) * 0.0001;
            Imgproc.approxPolyDP(approx, approxCurve, approxDistance, true);
            approxCurve.convertTo(approxContours.get(i), CvType.CV_32S);
        }
    }