| 摘要 |
PROBLEM TO BE SOLVED: To provide a printer of such one dot gradation step as 2-4 steps which copes with the gradation number exceeding 8 bit range with a threshold value not exceeding 8 bit. SOLUTION: A gradation correction means 7 expands an input pixel signal ni of one pixel 8 bit to expanded pixel signal ni' of one pixel nbit (n≥8). A threshold matrix 11 is provided that holds a threshold value nc of 7 bit range with 8 bit. The highest order bit of threshold value nc of 8 bit is made to hold an additional information related to arrangement of a threshold value. A threshold value expanding means 37 expands a low order 7 bit of nc to a threshold value nc' of nbit. The output range of the gradation correction means 7 is aligned with the range of expansion threshold value nc'. For each input pixel signal ni, an output gradation value to an output conversion table 22 is generated based on a differential valueΔn between the expansion threshold value nc' and the expansion pixel signal ni' corresponding to the threshold value nc selected sequentially as well as the value of highest order bit of the threshold value, to switch output laser pulses according to the additional information embedded in the highest order bit of the threshold value nc. COPYRIGHT: (C)2007,JPO&INPIT
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