Versatile moiré-free halftone geometry that uses frequency vector shearing
AssigneeXerox Corporation
InventorsShen-Ge Wang, Zhigang Fan, Robert Paul Loce
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Abstract
As set forth herein, computer-implemented methods and systems facilitate the generation of halftone screens for moiré-free color halftoning. A first fundamental frequency vector and a second fundamental frequency vector of a halftone cell are sheared using a selected shearing value. The shearing value is selected as an offset in a fast scanning or slow scanning direction. The selected shearing value satisfies various moiré-free conditions associated with the identified frequency vectors and is capable of being selected for multiple halftone screens. The halftone screens generated using the sheared frequency vectors are used for moiré-free halftoning.
Claims20
A computer-implemented method for generating halftone screens for moiré-free color halftoning, comprising:
- identifying a first color halftone screen having halftone cells defined by a first fundamental frequency vector (V1) and a second fundamental frequency vector (V2);
- selecting at least one shearing value (s) representative of an offset in at least one of a fast scan direction and a slow scan direction;
- shearing at least one of the first fundamental frequency vector (V1) and the second fundamental frequency vector (V2) for the first halftone screen by application of the shearing value (s) associated therewith;
- and
- generating a first sheared color halftone screen in accordance with at least one of the sheared first fundamental frequency vector (V1) and the second fundamental frequency vector (V2) so as to avoid moiré image effects.
A computer-implemented method for generating a set of sheared color halftone screens for moiré-free color halftoning, comprising:
- identifying a first color halftone screen having halftone cells defined by a first fundamental frequency vector (Vc1) and a second fundamental frequency vector (Vc2), a second color halftone screen defined by a first fundamental frequency vector (Vm1) and a second fundamental frequency vector (Vm2), and a third color halftone screen defined by a first fundamental vector (Vk1) and a second fundamental frequency vector (Vk2);
- selecting a shearing value (sc, sm, sk) corresponding to an offset in at least one of a fast scan direction and a slow scan direction for each of the first, second, and third color halftone screens;
- shearing at least one of the first fundamental frequency vectors (Vc1, Vm1, Vk1) and the second fundamental frequency vectors (Vc2, Vm2, Vk2) for each of the first, second, and third halftone screens by application of the shearing values (sc, sm, sk) corresponding thereto;
- generating a set of sheared color halftone screens in accordance with at least one of the sheared first fundamental frequency vectors (Vc1, Vm1, Vk1) and the second fundamental frequency vectors (Vc2, Vm2, Vk2) so as to avoid moiré image effects;
- and
- outputting the set of sheared color halftone screens.
A system that facilitates generating halftone screens for moiré-free color halftoning, comprising:
- a processor operable to:
- identify a first color halftone screen having halftone cells defined by a first fundamental frequency vector (V1) and a second fundamental frequency vector (V2),
- select at least one shearing value (s) representative of an offset in at least one of a fast scan direction and a slow scan direction, and
- shear at least one of the first fundamental frequency vector (V1) and the second fundamental frequency vector (V2) for the first halftone screen by application of the shearing value (s) associated therewith,
- generate a first sheared color halftone screen in accordance with at least one of the sheared first fundamental frequency vector (V1) and the second fundamental frequency vector (V2) so as to avoid moiré image effects;
- and
- a printer that prints a halftone image using the first sheared color halftone screen.
Dependencies are inferred from the claim text.