1. An image processing device comprising: input means for entering an image signal representing a density level of an image; memory means storing data for binary or multi-level encoding for each density level of the image, the data stored in said memory means being fixed-threshold-value processed data or halftone processed data; and means for addressing said memory means using the image signal entered by said input means as address data for said memory means, wherein said memory means is adapted to release the binary or multi-level encoded data corresponding to the density level of the image, by addressing said memory means by means of said addressing means, and wherein said memory means stores plural sets of data for binary or multi-level encoding corresponding to each density level of the image.