1. A method of estimating a halftone image comprising setting a unit area in a binary image consisting of black and white regions, shifting the unit area, and estimating the halftone image on the basis of a ratio of the white regions to the black regions within the unit area, wherein the binary image is a digital binary image, a number of white or black pixels within each unit area is counted while the unit area is shifted, and the halftone image is estimated on the basis of a count for each unit area.