1. An electronic apparatus for converting a multi-tone image into a two-tone image comprising: an original image memory having capacity for storing an original image; a threshold plane memory having at least enough capacity to store a threshold value for each of a number of areas of the original image memory; an output image memory having at least enough capacity to store a binarized image derived from an image stored in the original image memory; a dither memory having enough capacity to store values of a dither cell; means for applying the dither cell to the original image to generate pixels of a dither image; means for deriving representative density values from pixels of the dither image; means for determining a threshold value from representative values; and means for applying a threshold value to the original image to generate a two-tone image.