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Reading QR codes without a computer

qr.blinry.org

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Re: Reading QR codes without a computer

#31

Post by Retr0id »

subtra3t wrote: post #28
Retr0id wrote: post #26

Earlier quoted context omitted.

It doesn't matter how objectively good your camera/decoder is, in absolute terms. There will always be some minimum size or maximum distance, where the detail can no longer be resolved (or errors no longer corrected)

Why? Is this something that's a side effect of some irrefutable physics law or a limitation of the current technology?

Both. You can't have a measurable feature smaller than the Planck length, but that's not relevant to QR decoding in any practical sense.

As for the practical limits, try using your phone to take a picture of something very far away, or very tiny, and see what happens.

Re: Reading QR codes without a computer

#32

Post by ao98 »

Wonderful write up, thank you! One question I’ve been trying to answer: I’ve been seeing more QR codes in the wild using dots instead of squares, and rounded edges instead of hard corners.

All my research suggests these are reader implementation specific and not guaranteed to work per the official spec.

But I find it hard to believe these codes are becoming more prevalent if they aren’t guaranteed to read.

Anyone have more info on this?

Re: Reading QR codes without a computer

#33

Post by kqr »

ao98 wrote: post #32

Wonderful write up, thank you! One question I’ve been trying to answer: I’ve been seeing more QR codes in the wild using dots instead of squares, and rounded edges instead of hard corners. All my research suggests these are reader implementation specific and not guaranteed to work per the official spec. But I find it hard to believe these codes are becoming more prevalent if they aren’t guaranteed to read. Anyone hav…

You'd be surprised how incompetent most adults are at what they do. I'm sure some less technical person assumed QR reading works the same way everywhere, tested it with their device and went "Yess it works! Ship it!"

I also sometimes see QR codes that are inverted. Not all readers detect them but many enough do that they end up in print.

Re: Reading QR codes without a computer

#34

Post by TonyTrapp »

kqr wrote: post #33
ao98 wrote: post #32

Wonderful write up, thank you! One question I’ve been trying to answer: I’ve been seeing more QR codes in the wild using dots instead of squares, and rounded edges instead of hard corners. All my research suggests these are reader implementation specific and not guaranteed to work per the official spec. But I find it hard to believe these codes are becoming more prevalent if they aren’t guaranteed to read. Anyone hav…

You'd be surprised how incompetent most adults are at what they do. I'm sure some less technical person assumed QR reading works the same way everywhere, tested it with their device and went "Yess it works! Ship it!" I also sometimes see QR codes that are inverted. Not all readers detect them but many enough do that they end up in print.

That being said, the QR code readers most people have in their pockets already have to be able to deal with all sorts of problems (blurry pictures, dust on lens, and many more scenarios) that rounded corners are unlikely to have an affect on any of them.

Re: Reading QR codes without a computer

#35

Post by lights0123 »

ao98 wrote: post #32

Wonderful write up, thank you! One question I’ve been trying to answer: I’ve been seeing more QR codes in the wild using dots instead of squares, and rounded edges instead of hard corners. All my research suggests these are reader implementation specific and not guaranteed to work per the official spec. But I find it hard to believe these codes are becoming more prevalent if they aren’t guaranteed to read. Anyone hav…

In reality,

- Apple's barcode reader

- Google's ML Kit

- and ZXing, probably behind most third party QR code scanning apps

covers most QR code readers that users will actually use, so testing them is fairly easy.

Re: Reading QR codes without a computer

#37

Post by Aachen »

RugnirViking wrote: post #10
Aachen wrote: post #3

I tried reading them manually about ten years ago, but gave up because of the mask. The mask pattern needs to be applied (xor) before you can even tell as much as the data type... Does anyone know how much it actually helps QR code readers to have this mask pattern applied? Last month, I tried to find out what the optimal error correction setting is (answer: none, if the matrix isn't damaged, like in my use-case wher…

Last year I did some experimentation along these lines and I also found that no error correction was best, at least when 3d printing QR codes. I was trying to find how small I could print it and still have it be detectable. Like the sibling comment, I suspect it is because of individually larger pixels.

The problem with that, as I understand it, is that your 3d print (or any print or screen) cannot get damaged at all. The pixels being bigger makes it easier to scan ...when it's fully in view and fully intact. Any pixel fails, and you can never recover the original data (besides some guesses, e.g. if the protocol identifier gets damaged a la htwps://)

Error correction doesn't seem to be for easier scanning, but for errors that might occur

(... and stupid logo overlays)

but this information is annoyingly hard to find. Hence my question about the mask xor overlay: does that actually help? Did anyone try it, or did it just sound like a good idea?

Re: Reading QR codes without a computer

#38

Post by Isamu »

ao98 wrote: post #32

Wonderful write up, thank you! One question I’ve been trying to answer: I’ve been seeing more QR codes in the wild using dots instead of squares, and rounded edges instead of hard corners. All my research suggests these are reader implementation specific and not guaranteed to work per the official spec. But I find it hard to believe these codes are becoming more prevalent if they aren’t guaranteed to read. Anyone hav…

Rounded corners is handled similarly to blurry images, one of the main ideas is readers to be forgiving in what they accept, and rely on the error detection bits to tell if it is way off. With error correction you can tolerate stylistic mangling.
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