I would like to be able to have a medium-sized graphic file shown on a page. A much larger version of the same image would be on the server. When the user clicks on the thumbnail image, the area near the place where the mouse was clicked would be taken from the larger image and displayed below the thumbnail image. The page updating would be done with Javascript, but I need some way of cropping the large image and sending that to the browser. Is it possible to do such a thing with PHP, or would it require a CGI program?