1. A method for decomposing a particular pattern on a layer of a design layout into a set of images for generating multiple sub-patterns for multiple photolithographic operations, the method comprising: a) searching through a space of lithographically feasible images to identify a set of at least two images for decomposing the particular pattern; b) determining whether the union of the identified set of images adequately approximates the particular pattern; and c) repeating operations (a) and (b) until a particular set of images is identified that has a union that adequately approximates the particular pattern.