I remember a couple of years ago I read up about the details on how QR codes are created. Specifically the masks that are added at the end to ensure that there aren’t any areas with too much whitespace or something that ends up inadvertently looking like the corner of a QR code (that square inside a square thing).
And for some reason, I’m staring at two QR codes in front of me, looking at the details, one looks like it contains a pipe going around a corner, another looks like it has a bit of a star, which made me wonder… Why have I never seen a QR Code with a swastika or something else you really don’t want to have on there? I’ve never seen any word on filtering out stuff like that when it comes to masking.
Am I just too bored out of my mind so that I’m staring at QR Codes like this with way too much imagination or is there something I’m missing?
EDIT: I’m sure it’s possible to intentionally create one, I’m thinking more of accidentally creating one. Specifically when I see, for instance, a different QR code on the back of every seat in a train, for instance - you’re generating so many, no human is going to check that.
QR codes can have arbitrary looks even without dirty tricks (abusing the error correction to add a logo or taking advantage of central sampling to color all but the middle 3x3 square of each data pixel) but boy, is it hard.
Examples:
https://lemmy.sdf.org/post/31694735/18805217 (strings a long number in Number mode (3 decimal digits per 10 bits) to the URL, and somehow the resulting number turns out to be a small even number times a very high power of 2)
https://www.youtube.com/watch?v=qQkWjzqMbuA (uses padding bytes plus maybe some of that “intentional damage” in QR codes with logos)
OK, I was actually asking about accidental things, but this is pretty neat.
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