$jpegdata = $image->jpeg([$quality])
           This returns the image data in JPEG format.  You can
           then print it, pipe it to a display program, or write
           it to a file.  You may pass an optional quality score
           to jpeg() in order to control the JPEG quality.  This
           should be an integer between 0 and 100.  Higher qual-
           ity scores give larger files and better image quality.
           If you don't specify the quality, jpeg() will choose a
           good default.