As has been pointed out in another community, photoshop users can embed invisible QR codes as watermarks in images.

As has been pointed out in another community, photoshop users can embed invisible QR codes as watermarks in images. See https://goo.gl/Po2IVe Is there a way to do this without using photoshop? By the way, I enjoy seeing visible, non-intrusive ownership marks at the bottom of images when viewing shares, as I then can Google for more photos using that info should the poster fail to direct me to a photographer's home page. (Not that that ever happens!;-)
https://goo.gl/Po2IVe