Patent ID: 7221479

Claim:
A method for generating four-color images, comprising: associating three halftone screens with three color separations, where each screen comprises halftone cells specified by two spatial vectors, V n1 and V n2 , separated by an angle θ n , where n=a, b, c, where a, b, and c are three arbitrary color indices; where V n1 and V n2 have corresponding frequency vectors F n1 and F n2 associated therewith, and where the frequency vectors satisfy the following equations F a1 +F b1 +F c1 =0, and F a2 +F b2 +F c2 =0 where the subscripts 1 and 2 are arbitrary and interchangeable; associating a fourth halftone screen with a fourth color separation, wherein the fourth halftone screen comprises halftone cells specified by two vectors separated by the angle θ a , such that the two vectors have corresponding frequency vectors F a1 and F a2 associated therewith.