I once had an idea to generate "hidden" qr codes in art and photos. Initially I wanted to take a photo of a giraffe and replace one of its spots with a QR code, and hang it in my living room for guests to scan. It turned into this (broken) website: https://www.qraffe.com/. I don't have a lot of time right now to fix it. The pdf rendering is broken. If anyone likes this idea and wants to help with a PR, I'll be mighty appreciative. https://github.com/joeframbach/qraffe