| 摘要 |
PROBLEM TO BE SOLVED: To provide a halftone processing technique adopting dithering elements and error diffusion methodological elements in a manner different from the conventional art. SOLUTION: A printer 20 performs preliminary dithering processing by which a gray scale value of a target pixel and a dither mask 61 are compared in halftone processing. In the preliminary dithering processing, if the gray scale value has a threshold value THn_d of the dither mask 61 or greater, then a threshold value THe used in an error diffusion method is set to a low-level threshold THe_L, and if the gray scale value is no higher than the threshold value THn_d, then the threshold value THe is set to a high-level threshold value THe_H. Then, using the set threshold value THe, ON/OFF states for dots are determined by the error diffusion method. The low-level threshold value THe_L and high-level threshold value THe_H are stored in an error diffusion threshold value table 62 as values varying according to the gray scale value. COPYRIGHT: (C)2011,JPO&INPIT
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