This function saves an image of the current Genie screen so that a window can appear on top of it when using the showAsWindow() API.
Example Usage:
Place saveScreenImage() in the onload event of the Work With Spooled Files screen. Place showAsWindow() in the onpageload event of the Display Spooled File screen. When option 5 is selected to display a spooled file, it will now appear as a draggable window on top of the Work With Spooled Files screen.
