ZXing.Net: Scanned QR Code is not recognized
Hi,
I am having trouble with decoding the following QR code. The Code has been printed and then scanned again and can then no be read anymore by the ZXing library.
I mostly tried with the CommandLineDecoder and the WindowsFormsDemo from the Clients folder. I tried with all kinds of different settings but none seem to work.
What do I need to do to make this work?
Thanks for your help.
About this issue
- Original URL
- State: open
- Created 2 years ago
- Comments: 22 (1 by maintainers)
Hello, As I try to find an issue to trouble decoding Swiss QRCode (since days…)
–> I scan approx 50 Swiss Invoice to 300 dpi, color per day –> Mostly, the botom left pattern of the QR Code cause the problem (if you just make some manual colorisation of the botom left pattern, everytings become ok)
My solution (95% of my QR invoices are well decoded) –> first attemp --> crop (botom part of the page) + reduce image by 0.5 + TRY_HARDER + TRY_INVERSE (works almost always and fast) –> seconde attemp --> full page + no reduction + TRY_HARDER + TRY_INVERSE –> last attemp --> crop (botom part of the page) + enlarge image by 2 + TRY_HARDER + TRY_INVERSE
Not realy “nice” solution, but it works pretty well.
@n-exo I just now got to the point where I can fully decode a QR Code. I tried with your image. The problem seems to be that has a very low resolution. This makes it very sensitive to a not perfect detection of the alignment pattern. I might be able to improve upon it but I am not sure. What helps a lot though, is just scaling the image up (I tried with 500%):
The following images are debug output generated by my decoder. You can see that it detected the alignment marks fine, but because the calculated center is off a little, it doesn’t get the modules to the lower right correctly (and possibly others).
The scaled up version is perfect though (I did nothing special, just used paint.net and scaled it):
So the question is, why are your images of such a low resolution and can you do something about it? Maybe just scale it up before processing it?
@kltye I can confirm the suspicion about the alignment mark. My Decoder uses the lowest right mark and can decode your sample fine.
@kltye I just noticed that your last comment was potentially intended to be addressed to me. My answer is: I can’t / won’t. I’m not a .NET developer and busy improving the c++ port. Said improvements will result in the ability to scan the OPs Swiss code example with zxing-cpp.