public Canvas canvas() {
        Canvas canvas = new Canvas(getLowerBound(), getUpperBound());
        canvas.add(this);
        if (name != null) {
            canvas.setTitle(name);
        }
        return canvas;
    }
@Test
    public void testContour() throws Exception {
        System.out.println("Contour");

        var canvas = Heatmap.of(Z, 256).canvas();
        canvas.add(Contour.of(Z));
        canvas.window();
    }