| 摘要 |
<p>A dither mask for converting a continuous-tone image into a half-tone image is created by using a computer. A pixel array having a size corresponding to the dither mask to be created is defined and divided into a plurality of blocks (S1). An initial pixel value is so determined that the appearance frequency of the pixel value may be uniform for each block (S2). A pair of pixels to be exchanged are randomly selected from the pixels in one block, and the function value of a predetermined evaluation function representing the feature of pixel value arrangement of the pixels in the block are calculated for two cases in which the pixel values of the pixels are exchanged and not (S3). Whether or not the exchange is made is judged according to the result of comparison of the calculated values (S4, S5, S6). The exchange is made if the exchange is judged to be made (S7). The steps thus far described are repeated for all the blocks till a predetermined condition is satisfied (S8, S9, S10).</p> |
