Sudoku intersections with OpenCV in Java

import org.opencv.core.Mat;
import org.opencv.core.Core;
import org.opencv.core.Point;
import org.opencv.core.Scalar;
import org.opencv.imgcodecs.Imgcodecs;
import org.opencv.imgproc.Imgproc;

public class sudoku
{
    public static void main(String[] args)
    {
        System.loadLibrary(Core.NATIVE_LIBRARY_NAME);

        Mat image = Imgcodecs.imread("sudoku.png", Imgcodecs.CV_LOAD_IMAGE_COLOR);
        if ((image == null) || image.empty()) {
            System.out.println("Failed to load input image.");
            System.exit(-1);
        }

        int TILES_X = 9;
        int TILES_Y = 9;

        // Estimated point coordinates from sample image...
        Point p1 = new Point(110, 128);
        Point p2 = new Point(518, 49);
        Point p3 = new Point(187, 524);
        Point p4 = new Point(611, 428);

        // Vectors representing each edge of the puzzle
        Point dx_puzzle = new Point(p2.x - p1.x, p2.y - p1.y);
        Point dy_puzzle = new Point(p3.x - p1.x, p3.y - p1.y);

        // Scaled down vectors representing edge of a single tile
        Point dx_tile = new Point(dx_puzzle.x / TILES_X, dx_puzzle.y / TILES_X);
        Point dy_tile = new Point(dy_puzzle.x / TILES_Y, dy_puzzle.y / TILES_Y);

        System.out.println(String.format("dx_puzzle = %s", dx_puzzle));
        System.out.println(String.format("dy_puzzle = %s", dy_puzzle));
        System.out.println(String.format("dx_tile = %s", dx_tile));
        System.out.println(String.format("dy_tile = %s", dy_tile));

        for (int row = 0; row < (TILES_Y + 1); row++) {
            for (int col = 0; col < (TILES_X + 1); col++) {
                double x = Math.round(p1.x + dx_tile.x * col + dy_tile.x * row);
                double y = Math.round(p1.y + dx_tile.y * col + dy_tile.y * row);
                Point p = new Point(x, y);
                System.out.println(String.format("p[%d,%d] = %s", row, col, p));
                Imgproc.circle(image, p, 3, new Scalar(255,0,255));
            }
        }

         Imgcodecs.imwrite("sudoku_out.png", image);
    }
}