PURPOSE: To perform an intermediate binary-coding process between a character and a pattern unless discrimination between the character and pattern can not be made.

CONSTITUTION: A half-tone decision part 3 decides the extent (half-tone) of the processing of each of the picture elements of an input binary image as an intermediate element between the character and pattern. A half-tone power variation part 4 varies the half tone decided by the half-tone decision part 3 and a many-valued/binary conversion part 5 converts a character image or an artificial half-tone image by a dot concentration type dither method into a binary image by an artificial half-tone process having gradation characteristics close to a fixed threshold process and also converts other images by a density preservation type artificial half-tone process according to the decision result of the half-tone decision part 3.