A method for processing an input image including a plurality of input pixels each having a first number of possible input levels of optical densit y toform an output image including a plurality of separa tions each including a plurality of output pixels each having a second number of possible output levels of optical density. The method includes the steps of generating a fir st threshold reference signal as a function of the output levels of optical den sityof a plurality of corresponding pixels each being se lected from one of the plurality of separations, modifying a current one of the plurality of input pixels in a current one of the plurality of separations in accordance with an error signal derived by processing previous ones of pixels in the current one of t he plurality of separations, generating a second threshold reference signal according to the output levels of optical density of previously processed pixels in the current one of the plurality of separations, and forming one o f the output pixels by comparing the modified current one of the plurality of input pixels to the generated first threshold reference signal and the generated second threshold reference signal.
INTER-SEPARATION COLOR IMAGE PROCESSING USING ERROR DIFFUSION