PURPOSE: To print a surface pattern by a color printer which has an arbitrary resolution by calculating the number of dots, utilizing dither, and the number of repetition, which are capable of being expressed, from the densities of both the color printer to be used and yarn.
CONSTITUTION: The density M of warp and weft to be used, that is, the number of yarn per one inch, the array of the colors of the warp and weft, and the number of the warp and weft by color units are inputted to a control parts 1 by using a keyboard 7, and a tablet 8. Then, the number (d) of dots, a utilizing dither (z), and the number (k) of repetition are calculated from the density N (dot/inch) to be used and the density M(piece/inch) of the yarn to be used. Thus, the density of the yarn desired by users can be expressed.