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> On the QR topic, I don't understand how logos in the middle work. You are losing pixels and checks with the logo in the middle which is fine until you make the logo too big.

It is possible to add logos without (well, differently) abusing the error correction: https://research.swtch.com/qart

Of course most images in the middle aren’t doing that and rely on some level of error correction fixing it.

I love how dedicated some people are to hacking random things for fun. What a great read!

> particularly if you want them to look pretty.

I've been amazed at some of the QR codes I've seen in TV ads. Multiple subdirectories, plethora of parameters containing full city names and redundant zip codes, etc, resulting in massive QR codes that you can't even use from your couch because they're so dense.

> Given the amount of megapixels in any camera

It's not just that. It's the resolution of the display device too. It's brightness and whether that is causing bloom. If it's printed small, users may instinctively put the camera too close and it won't be able to focus. People have shaky hands and the image will have motion blur. Glare is a persistent problem with bikeshare apps, where the app turns on your phone's flashlight while scanning for nighttime use, but the QR code is glossy. Codes get scratched up, and the smaller the blocks are, the more they are degraded.

There really are tons of ways QR codes degrade no matter how many megapixels you have, and smaller codes are always going to be more resistant given the same overall physical size.

> Also related, imagine you wanted a HN QR code with 'Hacker News' written in the middle. This would work as a box in the middle but would be hard to read. So you can make a line across the middle rather than a box in the middle. This will break the QR code but not if you rotate the QR code 90 degrees first.

The outside (the parts between the alignment marks) have metadata, separated from the data by a dotted line. If your line touches the metadata that's bad. But as long as you stay within the data block any shape should work as long as you are not modifying more pixels than the chosen level of error correction can handle

Another fun thing are these stable diffusion/controlnet combinations which create QR codes that at the same are AI generated art. e.g. qrdiffusion or qrbtf