1. A system comprising: a display device; a programmable processor operable to execute computer program instructions; a storage device embodying instructions executable by the programmable processor to: display an electronic artwork having a plurality of layers on the display device, each layer including image data; receive an input selecting a layer in the electronic artwork, the image data of the selected layer including opacity data; automatically fit a shape to a perimeter boundary of a non-transparent region as determined from the opacity data, wherein the shape defines an area of the selected layer; assign an action to the area of the selected layer, the action defining a function that is to be activated when the area is selected; and associate the area and the action with the selected layer as a property of the selected layer in the electronic artwork.