private void showMatrix(AffineTransform at) {
        double[] matrix = new double[6];
        at.getMatrix(matrix);  // { m00 m10 m01 m11 m02 m12 }
        int[] loRow = {0, 0, 1};
        for (int i = 0; i < 2; i++) {
            System.out.print("[ ");
            for (int j = i; j < matrix.length; j += 2) {
                System.out.printf("%5.1f ", matrix[j]);
            }
            System.out.print("]\n");
        }
        System.out.print("[ ");
        for (int i = 0; i < loRow.length; i++) {
            System.out.printf("%3d   ", loRow[i]);
        }
        System.out.print("]\n");
        System.out.println("---------------------");
    }