PS(x,y)=PT(x,y)???PC(x,y)+(1???PT(x,y))???PZ(x,y) [0062] This equation is generally used for blending by using the ratio of the transparency. [0063] However, when there is a pattern such as a line and the like where the color changes abruptly in the background, there is a problem that the pattern is seen through the overlaid object O. As shown in the example shown in FIG. 4, in which the object is