A main vector: m^=(mx, my) and a sub-vector: s^=(sx, sy) determining cyclic structure of a basic matrix are defined, and a positional vector for a pixel configuring the basic matrix Pi^=(Pix, Piy) is defined, where the suffix i denotes an i-th pixel configuring the basic matrix. Then, the pixels configuring the basic matrix are arranged in such a manner as to satisfy the cyclic structure, and transformation of Pi^→Pi^+km^+ls^ is carried out where k and l are arbitrary integers, and may be negative values. Then a new shape of the basic matrix is obtained with Pi^+km^+ls^ as a new pixel positional vector Pi^.