PURPOSE:To improve image quality of pseudo multilevel image by suppressing the generation of specific texture by the cyclic application to a multilevel image. CONSTITUTION:In a threshold array preparation part 1, the pseudo multilevel image plane P (k) of an MXM pixels is defined as the solution of the reverse model of an optimum arrangement model and an evaluation expression V is minimized to determine the threshold array of the MXM pixel. Further, the multilevel value Pg of pseudo multilevel image plane chaging from '1' to '0' for each coordinate (x, y) is defined as the threshold Dxy of the coordinate (x, y). A threshold array [Dxy] is outputted to a threshold array storage part 2. In the threshold array storage part 2, the threshold array [Dxy] outputted from the threshold array preparation part 1 is stored. In a binarization processing part 3, the threshold Dxy is obtained by imparting the address (x, y) of the pixel of multilevel image IN to the threshold array storage part 2, a binarization processing is performed and a pseudo multilevel image OUT is outputted.
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