1. A method for improving image contrast achieved by a lithography process, the method comprising: receiving an integrated circuit (IC) design layout, wherein the IC design layout includes a target pattern to be formed on a workpiece; generating an exposure map based on the IC design layout, wherein the exposure map includes an exposure grid divided into dark pixels and bright pixels that combine to form the target pattern; and adjusting the exposure map to increase exposure dosage at edges of the target pattern, wherein the adjusting includes: locating an edge portion of the target pattern in the exposure map, wherein the edge portion has a corresponding bright pixel, and assigning exposure energy from at least one dark pixel to the corresponding bright pixel, thereby generating a modified exposure map.