public static Mat erode(Mat src, int erosionSize) {
    Mat dest = src.clone();
    int erodeType = 1; // CROSS
    Mat erodeKernel = Imgproc.getStructuringElement(erodeType,
        new Size(2 * erosionSize + 1, 2 * erosionSize + 1),
        new org.opencv.core.Point(erosionSize, erosionSize));
    Imgproc.erode(dest, dest, erodeKernel);
    return dest;
}