private int detectMotion(Mat motion, Mat result, Mat result_cropped,
            int x_start, int x_stop, int y_start, int y_stop,

            Scalar color) {

        int number_of_changes = 0;
        int min_x = motion.cols(), max_x = 0;
        int min_y = motion.rows(), max_y = 0;
        long startSysMillis = System.currentTimeMillis();
        // loop over image and detect changes
        for (int j = y_start; j < y_stop; j += 2) { // height
            for (int i = x_start; i < x_stop; i += 2) { // width
                // check if at pixel (j,i) intensity is equal to 255
                // this means that the pixel is different in the sequence
                // of images (prev_frame, current_frame, next_frame)

                int testme = (int) motion.get(j, i)[0];


                if (testme == 255) {
                    number_of_changes++;
                    if (min_x > i) {
                        min_x = i;
                    }
                    if (max_x < i) {
                        max_x = i;
                    }
                    if (min_y > j) {
                        min_y = j;
                    }
                    if (max_y < j) {
                        max_y = j;
                    }
                }
            }
            System.out.println((System.currentTimeMillis() - startSysMillis) + " millis");
        }
        if (number_of_changes > 0) {
            //check if not out of bounds
            if (min_x - 10 > 0) {
                min_x -= 10;
            }
            if (min_y - 10 > 0) {
                min_y -= 10;
            }
            if (max_x + 10 < result.cols() - 1) {
                max_x += 10;
            }
            if (max_y + 10 < result.rows() - 1) {
                max_y += 10;
            }
            // draw rectangle round the changed pixel
            Point x = new Point(min_x, min_y);
            Point y = new Point(max_x, max_y);
            Rect rect = new Rect(x, y);
            Mat cropped = new Mat(result, rect);
            cropped.copyTo(result_cropped);
            Imgproc.rectangle(result, x, y, color, 1);


            return number_of_changes;

        }

        return 0;
    }