Unable to read mirrored QR codes
vhtkrk opened this issue · 3 comments
Describe the bug
If a QR code is mirrored, zxing library is unable to read it.
To Reproduce
Try to scan a mirrored QR code, such as the attached one. At least qrfy.com seems to generate these out of the box.
Expected behavior
The QR code contents ("test2") scanned succesfully.
Screenshots
Desktop (please complete the following information):
- OS: MacOS 14 tested
- Browser: Chrome & Firefox tested
- Version: Chrome 126, Firefox 126
Smartphone (please complete the following information):
- Device: Samsung Galaxy Z Flip 5
- OS: Android 14
- Browser: Firefox
- Version: 126
Additional context
So I dug around the source and seems like on a failed scan zxing already tries to mirror the QR code, but is unsuccesful. This seemed perplexing so I dug around and it seems like the fault is at src/core/qrcode/decoder/BitMatrixParser.ts: in remask() if I change the line var dataMask = DataMask.values[this.parsedFormatInfo.getDataMask()]; to var dataMask = DataMask.values.get(this.parsedFormatInfo.getDataMask()); I'm able to read the mirrored code.
good catch! Can you create a PR?
I have to go for now but I'll get you a PR by tomorrow.
--> 0.21.1