METHOD FOR ROBUST ASYMMETRIC MODULATION SPATIAL MARKING WITH SPATIAL SUB-SAMPLING

摘要

The invention aims at providing a method for applying a spatial mark, that is invisible to the naked eye, on a medium. One constraint consists in allowing said mark to be scanned by a lower resolution image acquiring apparatus. Therefor, the invention provides a method for generating and applying on a medium a digital spatial mark of X x Y dots in accordance with a resolution of d1x by d1y dots per surface unit, provided that the ratio d1x/d2x and or d1y/d2y is more than 1, said method comprising the following steps: over-sampling the digital spatial mark in X based on a factor nx = d1x/d2x and in Y based on a factor ny = d1y/d2y; eroding the dots to be applied so as to leave one dot every nx dots in X and one dot every nx dots in Y; applying the spatial mark on the support.