In some examples, a computing device receives an image of an optically active article that includes a set of one or more symbols of a symbol set, wherein at least one symbol of the set of one or more symbols comprises a set of encoding regions that are embedded with the symbol. In response to receiving the image, the computing device may determine that a particular image region of the image represents the at least one symbol. For encoding regions within the at least one symbol, the computing device may determine, based at least in part on the determination that the particular image region of the image represents the at least one symbol, whether the one or more encoding regions are active or inactive. The computing device may perform, based at least in part on whether the one or more encoding regions are active or inactive, one or more operations.