| US 7,457,004 B2 | ||
| Halftone dot formation method, halftone dot formation apparatus, threshold matrix generation method used therefor and halftone dot recording medium | ||
| Hiroshi Asai, Kyoto (Japan); and Yasuhiro Takemoto, Kyoto (Japan) | ||
| Assigned to Dainippon Screen Mfg. Co., Ltd., Kyoto (Japan) | ||
| Filed on Oct. 27, 2004, as Appl. No. 10/973,446. | ||
| Claims priority of application No. P2003-369136 (JP), filed on Oct. 29, 2003. | ||
| Prior Publication US 2005/0094212 A1, May 05, 2005 | ||
| Int. Cl. H04N 1/405 (2006.01); H04N 1/409 (2006.01) | ||
| U.S. Cl. 358—3.06 [358/3.13] | 15 Claims |
| 1. A halftone dot formation method for forming halftone dots used to represent an original image of gray scale, comprising
the steps of:
a) arranging a plurality of halftone cells in irregular shapes at random and dividing said plurality of halftone cells into
a plurality of groups each consisting of halftone cells which are distributed uniformly; and
b) forming halftone dots on the basis of an original image with said plurality of groups having different dot growth speeds
each of which corresponds to the amount of variation of a dot area in a halftone cell with respect to the amount of variation
in gray level of said original image, wherein
halftone cells belonging to one of said plurality of groups which consists of a minimum number of halftone cells are so arranged
as not to be adjacent to one another, each having a larger area and a higher dot growth speed as compared with halftone cells
belonging to other groups.
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