1. A method of dynamically constructing a rasterizer comprising: selecting a base rasterizer; obtaining parameters describing the base rasterizer; obtaining at least one replacement block of code; allocating memory for a dynamically constructed rasterizer; copying the base rasterizer into the memory allocated for the dynamically constructed rasterizer; and copying the at least one replacement block into the base rasterizer stored in the memory using the parameters to form the dynamically constructed rasterizer.