An image processing system and method using the technique of halftoning. It first inputs into a second printer the image color scale data of a standard color test chart, on which the second printer performs halftoning using its built-in halftone table, in order to output a set of second image color level data. Next, it obtains a host printer function according to the image color scale data and the second image color level data and then establishes a correlation function between the host printer function and the standard function, according to which the halftone table is modified to become a dithered halftone table, bringing the subsequent print quality of the second printer closer to that of the standard function.