1. An image processing apparatus comprising: means for fetching an image; means for forming a density histogram based on the fetched image; means for deciding a sort of the fetched image corresponding to a histogram distribution of a background area when the density histogram is divided into the background area and a character area having an image density higher than the background area, a first image density frequency having a maximum frequency within a range of the background area, and each frequency of the density histogram in left and right sides of a crest having the first image density frequency; and means for correcting a gradation of the fetched image, in accordance with a decision result of the deciding means.