1. A method of manufacturing an integrated circuit comprising: providing a target design, wherein said target design has an target image shape divided into target segments and each of said target segments has an associated segment evaluation point; providing an initial mask shape; dividing said mask shape into mask segments corresponding to each of said target segments; determining a simulated image corresponding to each of said associated segment evaluation points, wherein said simulated image is formed in accordance with said mask shape for a lithographic process; providing a deviation tolerance for a deviation of a simulated image metric from a corresponding target image metric; and for each of said segment evaluation points, determining a simulated image metric based on said simulated image at said segment evaluation point, and refining the mask segment corresponding to said segment evaluation point if said simulated image metric exceeds said deviation tolerance.