| 摘要 |
PROBLEM TO BE SOLVED: To obtain a resolution converter suppressing the generation of moire with respect to even a halftone picture by detecting a pixel corresponding to the maximum area of the divided area of the grid of a conversion pixel to control a threshold value by each pixel. SOLUTION: The threshold value is decided by the maximum value max [Sij] of an area Sij within a generated grid and the color of a pixel (dominating symbol) corresponding to it in order to store isolated black pixels and white pixels. For example, max [Sij]=S001 is formed and Pj, i is a black pixel. As an area of the generated grid Pj, i is projected to is S00, if the theshold value is made slightly lower than S00 to be S00-ε, the generated pixel becomes a black pixel to store Pj,i. Then, ε is a small positive number. By thinking similarly, at the time of supposing an original is 256-gradation when Pj, i is a white pixel, it is satisfactory to make the threshold value 255-[max [Sij]-ε]. Consequently, the black and white isolated points are stored, the gradation of the halftone picture is not lost even at the time of being slightly reduced in size. |
