PURPOSE: To prevent thickness of a line from thinning by unifying, which is composed of a two-dot array like especially en-size character mixed in an em-size character among lines after reducing a character font composed of a dot matrix pattern by a reducing algorithm.

CONSTITUTION: A dot array on the first line is formed by the first OR means and the dot array on the last (n+1)th line is respectively formed by a selective means. Further, an intermediate dot array is formed by the second OR means which acts on the character pattern of a four or more dot array. Thereby, the dot array of a dot pattern after reduction becomes the dot array of two or more dots. A line composed by the two-dot array like an en-size character mixed in an em-size character is composed of the two-dot array even after reduction, and thickness of the line to be printed is unified.