many openCV algorithms for face/licence plate detection start with very simple extractors to determine whether there is a feature of interest or not - therefor some "scramling" with noisy image will not be trivial.

Then it often goes pretty sophisticated, so your crasher would need to be in good allignment with particular algorithm.

Therefore my simple and rough answer would be: it's difficult, and if it will work - it will be only for a particular (or close family) algorithm

Dear Cem Onat Karagun,

Look your answer in applications of Mathematical Morphology in image processing.