To provide a method and device for clipping an object for a non- rectangular polygon at a high speed and with relatively small memory using amounts (at low costs).

A non-rectangular clipping path(CP) is defined for an original page (901). Next, a rectangular boundary called a mosaic buffer 20 whose width and height are exactly the same as those of the boundary area of the non- rectangular clipping path. (902). All objects for the CP are clipped to the mosaic buffer (MB) by using a high speed rectangle clipping processing (903 and 904). After all the objects are chipped to the non-rectangular clipping path, the mosaic buffer is converted into a pattern buffer (PB) (905). At last, the content of the PB is clipped to the original clipping path (906).