Error: QR code could not be decoded


i jus tried to scan the code with iOS, this works.

can you give more details about used platforms (both android?) and versions? and also test if things work for a non-emoji-only-name for that set up?

nb: welcome aboard!

I had also some time ago this problem trying to use a account. I gave up finally. Could maybe a mirror problem. Sometimes I saw on my desktop camera the QR code mirrored. But I found no way to change this. Could als be another problem.

Using 1.42.6 on Android 11

I scanned by importing the above image file from gallery, not using camera. It works for some emoji and alphabet.

Maybe we should stop overlaying avatar on top of the QR code. This looks nice, but actually makes scanning the code harder.

I wonder if it would help to make the background 100% white. I like the emoji option, it looks cool. Also recommend that importing from gallery does not trigger camera permission dialog.

1 Like

White background should definitely help.

It is already white on Android, so grey background is a Desktop issue.
Opened an issue: Make QR code background white · Issue #3673 · deltachat/deltachat-desktop · GitHub

it is an svg generated by core, also desktop can scan it, so I’d blame the scanner library on android, there I would assume it has sth to do with the blurring/compression in the image?

GitHub - dignifiedquire/quircs: qrcode scanner in rust - ported from quirc detects it no problem:

quircs test program
Library version: 0.10.2

                                      Time (ms)        Count   
  Filename                        Load  ID    Total ID    Dec  
  0be882ad3845edc1c7b5b632bd80b67ba1f94a10.png  41    20    62    1     1    

  Decode successful:
    Version: 8
    ECC level: M
    Mask: 6
    Data type: Some(Byte)
    Length: 126
    Payload: Ok("")
    ECI: None

I doubt that, I’d guess that would be a svg rendering bug or more likely you using a dark theme so it appears whiter than it actually is.

Theme = dark, Wallpaper = default

As you can see from the github issue we are not really able to reproduce your problem. It would be easy to change the background color, but we are not sure if that really helps. I have replaced the previous color (f2f2f2) with ffffff in this image, can you try to scan it?


I have looked up an article with evaluation of Quirc, ZXing and ZBar based on a dataset with 286 QR codes: Identification of QR Code Perspective Distortion Based on Edge Directions and Edge Projections Analysis - PMC

ZXing that we use on Android is the worst, Quirc is only slightly better (40% success rate), while ZBar (GitHub - mchehab/zbar: ZBar is an open source software suite for reading bar codes from various sources, including webcams. As its development stopped in 2012, I took the task of keeping it updated with the V4L2 API. This is the main repository for it. There's a clone at at, and another one at gitlab.) succeeds in 92% of the dataset images.
Quirc is apparently not very good even at scanning non-photo images and mistakes large black areas for corners with its floodfill algorithm in the first step: fake capstones · Issue #126 · dlbeer/quirc · GitHub

So if we replace QR code scanning library on Android we should switch to ZBar.
Android also has built-in QR code scanning API, but as far as I understand it is non-free and is not available on systems without Google Play services: اسکن بارکد  |  ML Kit  |  Google for Developers