| 摘要 |
The present invention produces halftone dots which shows small fluctuations in area irrespective of variation of the relative position of the address range of screen pattern data against the pixels. a plurality of exposure-decision points RC, SP1, SP2, and SP3 are set for each pixel RP. Screen pattern data is compared with an image signal at each of the exposure-decision points, and the results of comparison are output as preliminary decision value. The preliminary decision value is summed up to make total value Tex for each pixel, and the total value Tex is further accumulated in a primary scanning direction U to make total-sum value SIGMA Tex. When the total-sum value SIGMA Tex for a pixel is equal to or greater than the number of exposure-decision points, the pixel is determined to be exposed, and carry-over data Dco, which is obtained by subtracting the number of the exposure-decision points from the total-sum value SIGMA Tex, is transferred to the next pixel. When the total-sum value SIGMA Tex for a pixel is less than the number of the exposure-decision points, the pixel is determined not to be exposed, and the total-sum value SIGMA Tex is transferred to the next pixel as the carry-over data Dco.
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