Although the patterns (G), (H) shown in FIG. 5 have been used in this embodiment, other patterns can be used to produce similar effects if they comprise a combination of two types of patterns that can be combined together at their respective ends, each of the patterns including at one end one subpixel to which a weight of 1/2 is applied and at the other end two subpixels to which a weight of 1/2 i