Patent ID: 7542599

Claim:
A method for reducing a number of shapes performed a computer system, said method comprising the steps of: forming a first shape pattern; forming a second shape pattern, wherein the second shape pattern consists of all of the first shape pattern and error shapes; extracting the error shapes from the second shape pattern; deriving from a subset of the extracted error shapes at least one environment shape corresponding to each error shape in the subset of the error shapes, said environment shape reflecting a local geometric environment of its corresponding error shape; and deleting a subset of the environment shapes such that only a plurality of unique environment shapes satisfying a selection criterion remain subject to the remaining unique environment shapes differing from each other with respect to a geometrical characteristic of their respective geometric shapes; wherein the deriving step comprises expanding each error shape in the subset to form a corresponding expanded shape and forming the at least one environment shape corresponding to each expanded shape by removing all portions of the expanded shape which are common to the second shape pattern; wherein each error shape in the subset has a polygonal shape; wherein expanding the first error shape comprises outwardly projecting each bounding side of the error share by a distance in a direction perpendicular to the bounding side; wherein the distance is a same first distance for each bounding side oriented in a first direction for a first error shape of the error shapes in the subset; wherein the distance is a same second distance for each bounding side oriented in a second direction for the first error shape; wherein the second direction is orthogonal to the first direction; and wherein the same first distance is unequal to the same second distance.