If I have a cubic Bezier curve specified by two endpoints and two control points, how can I find an offset curve which is "parallel" to the original at some given distance, after i have determined the other 2 endpoints ? The red dots in the image http://s11.postimg.org/n44nmqzoj/bezier_question.png are the endpoints, and the red squares are the control points of the initial bezier segment. Everything red is known, and i need to find the blue squares, that is, the control points of the second curve, such that the second curve is parallel to the first one(must also take into account that the dimension varies, as if it was below the original bezier, the second curve would be smaller).

I am sorry for the graphics of the image, it has only a illustrative purpose and i am not good at drawing. Thank you for the help!