A posteriori scaling of run length encoded polygons

Scaling run-length encoded binary patterns is quite useful in some instances of computer graphics, such as phototypesetting with variable-sized characters. A very simple method can be used to perform the scaling, which separates scaling along the direction of the runs and along the perpendicular. This method, herein called a posteriori scaling, has the drawback of adding noise to the original pattern. After reviewing the method itself, we derive several mathematical results to better understand known characteristics of the noise, taking polygons as test patterns.