In electron beam lithography, an apparatus and method decompose rectangles at the exterior of a desired electron beam exposure pattern into portions having a substantially constant environment. This process also includes sorting of rectangles into bands in order of addresses of the rectangles and the assignment of labels or tags to the resulting rectangles indicating the edge(s) of the rectangle at which cuts were made to form the rectangle. When these rectangles are further decomposed by increment cutting and processes to receive exposure doses corrected by mutual proximity effects, including recombination of rectangles having the same assigned exposure dose, improved location of cut boundaries is achieved. Overexposure and resultant blooming of the pattern is prevented and exposure dose is assigned with higher accuracy since any averaging of exposure dose will be over a region having a substantially constant environment of neighboring shapes. Additionally, by ordering of the shapes, and cutting (with recombination) in plural steps, data carried forward in subsequent processing is reduced and accumulation of exposure correction information is facilitated.