Restrict the Move of objects in area

I am setting an image as background. it is being set from 0,0. is there a way an object placed over the layout can not be moved beyond the boundaries of that image which is set as background.

            { layerName: "Background", position: new go.Point(0, 0),
              selectable: false, pickable: false },
            $(go.Picture, "abcd.jpg")

Right now i can move the object which was placed at 0,0 to -20,-20 or beyond the co-ordinates of the image.

Yes, see this example. It uses Diagram.fixedBounds and a Part.dragComputation function to keep the nodes within an area.

Thanks it is working.