This QR code is unreadable, why?

[frederikhors]

This is unreadable, why?

Thanks for you amazing work!

[hschimke]

Hmm, interesting. it doesn't read for me, but when I tried taking a screenshot of the image instead of just reading it directly it worked. Very odd behavior. I suspect that it has to do with the size of the image and the noise level giving it a hard time. I'll play with it some, not sure if it's a bug or just unexpected behavior.

[frederikhors]

when I tried taking a screenshot of the image instead of just reading it

What do you mean?

[hschimke]

This image scans without issue (with TryHarder). It’s a screen shot of the barcode on my phone. Trying the image directly fails.

…

On Sat, Jan 31, 2026 at 14:30 frederikhors ***@***.***> wrote: *frederikhors* left a comment (rxing-core/rxing#74) <#74 (comment)> when I tried taking a screenshot of the image instead of just reading it What do you mean? — Reply to this email directly, view it on GitHub <#74 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AADHR7KWMEU7DXYC23OSZCL4JUGG7AVCNFSM6AAAAACTOBTIKOVHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZTQMRZGI4TCNZXGE> . You are receiving this because you were assigned.Message ID: ***@***.***>

[hschimke]

Apologies! My image failed to upload.

[frederikhors]

Can you better explain what you wrote, @hschimke?

I don't understand. Can rxing read this QR code?

I tried with this:

let result = rxing::helpers::detect_in_file(
    file_path,
    Some(rxing::BarcodeFormat::QR_CODE),
)

and I also tried with:

let mut possible_formats = HashSet::new();

possible_formats.insert(BarcodeFormat::QR_CODE);

let result = rxing::helpers::detect_in_file_with_hints(
    file_path,

    Some(rxing::BarcodeFormat::QR_CODE),

    &mut DecodeHints {
        TryHarder: Some(true),
        PossibleFormats: Some(possible_formats),
        AlsoInverted: Some(true),
        ..Default::default()
    },
)

But nothing works with that qrcode.

[hschimke]

Apologies for the poorly worded response!

The image is unreadable by the library as is. It appears that if it is padded and zoomed out a little the subsequent image is readable.

So, the symbol is readable but the image is not.

My high level guess is that because of the tight crop and the rotation of the symbol that there is a problem when the image is rotated, this would explain why padding seems to make the image readable.

I will investigate this when I have a chance, but the simple answer is: the image is not readable, the symbol is. Try padding with white and reading again.

Let me know if that makes sense.

[frederikhors]

Excuse my ignorance, what is the "symbol"?

I've already tried padding and it doesn't work, but maybe I'm doing it wrong.

Thanks for your work!

[hschimke]

The symbol refers to the actual barcode, just more generally.

Is the contents: {removed}

I’ll look into it when I get back to my computer, I haven’t had a chance to run it through the debugger yet to see where it fails.

It’s also possible that it is failing error correction, the image is fairly noisy.

[frederikhors]

Okay, thanks. Could you please edit the previous post to remove the content (the symbol) to prevent it from being indexed on the web?

Thanks again.

[eventualbuddha]

Linking to relevant issues in other Rust QR code libraries:

• This QR code is unreadable, why? WanzenBug/rqrr#49
• QR codes with very small modules in a larger image are not detected eventualbuddha/zedbar#32 (disclaimer: this is my repo)

[hschimke]

Linking to relevant issues in other Rust QR code libraries:

• This QR code is unreadable, why? WanzenBug/rqrr#49
• QR codes with very small modules in a larger image are not detected eventualbuddha/zedbar#32 (disclaimer: this is my repo)

Thank you for this. Seems like a good addition.

[hschimke]

@frederikhors The version in the repository, likely to launch as 0.9.1 in a few days, should include a few fixes to work with the image you supplied. I noticed in some of the linked threads other people posted here that many of the fixes only worked with a handful of your images. I'd be happy to take a look at them if they don't work with this update. I'll post here again when I release the next version.

[hschimke]

@frederikhors v0.9.1 has been published. The latest version of https://scan.rxing.org can now decode the original image as long as "filter input" is selected. I am not sure how it will behave with other images of that size/quality. I'm going to close for now, but please re-open if you find more images for me to test against.