A process for the gradation control and to the image quality improvement in a thermal printer

摘要

A gradation control method in a color thermal transfer printer is adapted to express one pixel by a dot matrix with two rows and two columns, control a density value of one dot with a time for energizing a heating element (19) of a thermal head (1), and carry out mask patterning for plotting only one of four dots when the gradation of each color for one pixel is not more than a prescribed value while plotting only two of the four dots when the gradation is in excess of the prescribed value. At this time, employed is a mask pattern of necessarily plotting cyan and magenta on dots which are different from each other.;A picture quality improving method in a staggered printing system is adapted to plot a noted dot (E) when at least one of such conditions that density data of the noted dot (E) is in excess of a prescribed density value and that density data of any of four dots (B, D, E, H) most approximate to the noted dot (E) is not more than a prescribed low density value is satisfied, even if the noted dot (E) corresponds to that to be masked.