To provide a method for judging character size with which a problem of image quality deterioration by nonuniformity of judgment is eliminated and sure improvement of image quality is obtained when performing prescribed image processing to small characters in comparison with the case of judging the character size by bounding box size of individual characters.

The method judges the character size in order to perform optional image processing to characters below the fixed size in a page description language in which a glyph coordinate space expressing positions of control points constituting outlines of the characters and a device coordinate space expressing pixel positions in an output device are linked by a plurality of affine transformation matrixes, and judges the character size to a reference rectangle in the glyph coordinate space by whether or not area of a rectangle on the device coordinate space as a result of performing coordinate transformation by the plurality of affine transformation matrixes is below a prescribed value.