Generating a QR code with only ARM Assembly

Re:Generating a QR code with only ARM Assembly by gregsadetsky on Wednesday September 08, 2021 @04:29PM (#28462632)

Fascinating, thanks a lot for these.

Scandit and Cognex have iOS apps, and Aspose has a web recognizer demo.

I tried all three with a 2D QR code (my vax card!) from which I truncated ~2-3 bit-"rows" from the bottom. None of the apps/site detected the code.

This is truly not a thorough test -- the 2D rows may be more information-dense than I think i.e. they are not recoverable using the built-in error correction (basically I'm removing too much information -- the equivalent of a long/deep scratch on a CD).

I'm just trying to get an intuitive sense of how much damage a QR code can sustain and ... I guess if there's such a thing as QR code forensics (there must be...??) for decoding partial codes versus not detecting "anything".

Thanks again for the links. Super interesting space

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Re:Generating a QR code with only ARM Assembly by jhugo on Wednesday September 08, 2021 @07:42PM (#28464411)

When generating a QR code, you can decide how much redundancy to include, making the QR larger for the same data but more resilient to "scratches".

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Re:Generating a QR code with only ARM Assembly by gregsadetsky on Wednesday September 08, 2021 @07:52PM (#28464485)

Thanks. Looking into it [0], the QR code I'm testing uses the "up to 7% damage" error correction level L, which makes sense since there's already a lot of data being packed in the (vax proof) code.

... I still want to find a debugging/verbose QR decoder :-)

[0] https://blog.qrstuff.com/2011/12/14/qr-code-error-correction

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