Provided is a method of transforming an integrated circuit (IC) pattern into one or more patterns suitable for subsequent processing, such as mask fabrication. The method includes receiving an IC pattern that has an arbitrary shape, and using a computer, deriving an approximation IC pattern, wherein the approximation IC pattern is in a shape that is a user-defined fabrication-friendly shape, such as a rectangle or an ellipse. The method further includes calculating a pattern approximation error between the IC pattern and the approximation IC pattern. The method further includes checking whether the pattern approximation error is less than a user-defined threshold. If it is, the method further includes outputting the approximation IC pattern for subsequent fabrication. Otherwise, the method further includes splitting the IC pattern into a plurality of subparts, and recursively transforming each of the plurality of subparts.