Each of the N nontransparent images includes an intersecting area with one of the M transparent images, P is an integer larger than 0, M is an integer larger than 0 and smaller than or equal to P, N is an integer larger than or equal to 0 and smaller than P, and P=M+N. The method also comprises determining a page-level transparent area and a page-level de-transparentizing area of the P graphic ent