| 摘要 |
PURPOSE: To prevent occurrence of the moire fringes by deciding alternately the threshold value which are allocated to the pixels included in dot cells of the shadow point centers. CONSTITUTION: A supercell is divided into dot cells Hh of the highlight point centers and also into the dot cells Hs of the shadow point centers. The threshold value 0, 1, 2, 3... which are allocated to the pixels included in cells Hh of the highlight point centers and the threshold value N, N-1, N-2, N-3... which are allocated to the pixels included in cells Hs of the shadow point centers are alternately decided (in order of 0→N→1→N-1→...→3→N-3). As a result, the number of blackened pixels included in the cells Hh is equal to the number of white-on-black pixels included in the cells Hs in terms of every dot cell included in the supercell S when an original image has high density. Thus it is possible to prevent the moire fringes that are caused by the periodical changes of the number of blackened pixels included in the dot cells. |
