CONTINUOUS IMAGE ESTIMATION METHOD

A continuous image estimation method of a binary image wherein only one scanning aperture satisfying a predetermined condition for each picture element of a continuous image to be estimated from a plurality of scanning apertures for each kind in a dither image formed of a dither matrix, and the continuous image is estimated on the basis of the number of white or black picture elements in the scanning aperture selected. The predetermined condition is that a gradation expression is conducted in a lower spatial frequency range by using larger scanning apertures and in a higher spatial frequency range by using smaller scanning apertures, and that for the coincidence between patterns of a dither image in the scanning aperture and a binary image, which is made binary with the dither matrix from a continuous image formed on the bases of the number of the white or black picture elements in the scanning aperture, the patterns being obtained by comparing the dither image and the binary image for each aperture.