public static void point(double x, double y) {
        double xs = scaleX(x);
        double ys = scaleY(y);
        double r = penRadius;
        float scaledPenRadius = (float) (r * DEFAULT_SIZE);

        // double ws = factorX(2*r);
        // double hs = factorY(2*r);
        // if (ws <= 1 && hs <= 1) pixel(x, y);
        if (scaledPenRadius <= 1) pixel(x, y);
        else offscreen.fill(new Ellipse2D.Double(xs - scaledPenRadius/2, ys - scaledPenRadius/2,
                                                 scaledPenRadius, scaledPenRadius));
        draw();
    }