num.align_to (X_AXIS, CENTER);
num.translate_axis (w/2, X_AXIS);
num.align_to (Y_AXIS, CENTER);
num.translate_axis ((ry-ly)/2, Y_AXIS);
num.align_to (X_AXIS, CENTER);
num.translate_axis (w/2, X_AXIS);
num.align_to (Y_AXIS, CENTER);
num.translate_axis ((ry-ly)/2, Y_AXIS);