| 摘要 |
A multilevel ink jet printer of the present invention has a greater number of tone values expressible in the respective pixels included in an image and effectively prevents the occurrence of banding. The ink jet printer of the invention enables successive ejection of ink droplets in each pixel in the course of main scan. The number of times of ink ejection in each pixel is set according to the tone value expressed in the pixel. The technique of the present invention shifts the hitting positions of the successively ejected ink droplets in a main scanning direction and thereby creates a flat dot having a longitudinal axis in the main scanning direction. The dot pitch in a sub-scanning direction is set to be sufficiently smaller than a dimension of the flat dot in the sub-scanning direction. The dot pitch in the main scanning direction is, on the other hand, set to be sufficiently smaller than a dimension of the flat dot in the main scanning direction, in such a manner that the total number of pixels included in the image does not exceed a predetermined value, which is specified according to a printing speed. Creation of dots at the preset dot pitches enables an image having rich tone expression to be printed at a high speed without causing the banding.
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