Graphical definition of start/stop frame for Ken Burns transition

It would be good to define the start and stop frame for a Ken Burns transition on a image graphically by placing a start and a stop rectangle on the image and path from specific corner (top left for example) which describes how the pan and zoom should be done. As first implementation straight paths with constant speed is enough but I see that we could improve later by adding curved paths with rotation of the image and also have different speeds along the path (but with constant acceleration/deacceleration) between the time points on the path.