This reminds me of an early-2000s product (maybe earlier? Not sure) which used a frequency-domain manipulation of some sort to overlay a watermark on physical

This reminds me of an early-2000s product (maybe earlier? Not sure) which used a frequency-domain manipulation of some sort to overlay a watermark on physical print. The idea was you could point your webcam at a magazine page and be whisked off to some website or other. It pre-dated the ubiquity of QR codes, and it was diffuse across the entire page rather than being a discrete visual element. It probably died off because not enough people had webcams and nobody had the custom software installed. It came to mind because the `Watermarked x_t` image on page two reminds me of the overlaid noise pattern, which you could just make out on the page. I think they must have been doing something similar in frequency space. Is this ringing any bells for anyone? I've tried googling but I just can't find evidence of it ever existing.