Patent US 5,081,691

A digital filter for a digitized graphic image which eliminates border aberrations in the transition from one color to another in the image, which eliminates isolated dots while retaining isolated background in the center of alphanumeric characters, provides uniform coloration of half tone areas, corrects error colors to a predetermined color and selectively provides mode filtering on the digitized signal. Prior to any filtering of digitized signals, sets of predetermined colors for half tone, solids, errors and thresholds for various logic functions of the filter are established. The filter then converts each pixel in an array to a different color or maintains its color dependent on logical processing in several levels of selectively branching logic.