1. An image processing apparatus, to which an image including a line pattern such as a character, a ruled line, a graphic, etc. is input, outputting a corresponding binary image, comprising: a slightly indistinct binary image generating unit generating a first image that includes almost an entire shape of a line pattern although the shape is indistinct; a shape-preserved binary image generating unit generating a second image that includes almost the entire shape of the line pattern and also includes noise in a background area other than a neighborhood of the line pattern; and an image combining unit combining the first and the second images for each pixel, and generating a satisfactory binary image that includes almost the entire shape of the line pattern while preserving the shape and does not include the noise in the background area.