1. A method implemented on a user interface incorporated in a computer system coupled with a scanner for performing an automatic scan operation on an original document, the computer system running a scanner driver and an application program; the method comprising the steps of: storing a set of default image processing settings in the user interface; activating the scanner to perform a primitive scan operation on the original document based on the default image processing settings to thereby obtain a primitive scanned image which is then transferred to the scanner driver; activating the scanner driver to perform a set of image processing routines on the primitive scanned image to thereby obtain the image qualities of the original document; and based on the image qualities of the original document, specifying a set of suited image processing settings for optimal scan of the original document; and activating the scanner to perform a final scan operation on the original document based on the suited image processing settings to thereby obtain a final scanned image which is transferred to the application program for use by the application program.