| 摘要 |
Ink is transferred to an image receiving paper by a thermal head having a plurality of heating elements. The tonal level of a half tone image is expressed by the size of an ink dot recorded in a print pixel. The pixel density is changed in accordance with a smoothness of the surface of an image receiving paper and an image density. The size of a print pixel becomes large as the image density becomes low. If a high quality image receiving paper having a smooth image receiving surface is used, one ink dot per one print pixel is recorded by driving one heating element independently from the image density. If a standard paper having a round image receiving surface is used, for a highlight image area, three consecutive heating elements are driven at the same time to record a large size ink dot in a large size print pixel so as to ensure a reliable ink dot transfer. For a middle-to-high image density area, two consecutive heating elements are driven at the same time to record a middle size ink dot in a middle size print pixel. If a rough paper is used, four consecutive heating elements are driven at the same time at a highlight image area, and three consecutive heating elements are driven at the same time for a middle-to-high image density area.
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