I'd suggest you give your actor (I suppose you use Scene2D) a bigger size, than your Image.
If you dont use Scene2D I recommend that you watch into it, because that would is the best way I can imagine to do such a game.
But as a final answer on your question: add transparency to your Image at the border. (which would go quite easy for once, but changing it would be a hell.
Or you try to use a Container. As example use Stack from Scene2D. You can place a bigger Image, which is transparent and on top of this Image a smaller one.
Now you can scale your padding, or your Image, as you want.