Embedding data in printed image features on a receiver printed with an offset printing process includes a first offset printing member for forming an image on the first offset printing member. According to the present invention, the spray blocking object is a strip, the cross-sectional profile of the strip being fully open in the direction of an axis in a cross-sectional plane of the strip, and the strip is placed on the already deposited layer with said axis directed substantially parallel to the direction of the incident metal spray. A Rom logic circuit receives an instruction read from the read only memory and produces a group of output signals dependent upon the instruction.