Make QR code background white

[link2xt]

This should make scanning it easier, currently it is black on gray.

See discussion on https://support.delta.chat/t/error-qr-code-could-not-be-decoded/2923/6

[Simon-Laux]

if this is an issue it would be a core issue, because the svg is generated there (I don't think desktop modifies it in any way).

But as I said in the forum I think this should be treated as a problem in the android scanning library, maybe additionally make a pass with https://github.com/dignifiedquire/quircs/tree/master when updating or changing settings does not help.

[link2xt]

I think in the core it is transparent, because on Android background is white.

[link2xt]

But we can also add a white rectangle behind in the core.

[r10s]

it is a very light gray also on ios, tbh, nothing that should disturb, there is still lots of contrast. maybe a very bad qr code scanner?

before making things less nice, we should test by gimp-fill-with-white if that really helps on the issue reported in the forum.

esp. as also avatar and mirroring is mentioned as possible causes.

[link2xt]

maybe a very bad qr code scanner?

Android QR code scanning library is very bad at scanning, yes.

[Raiden-GH]

My inexpensive Android phone sometimes also has problems with QR codes.
After one or two attempts, it works. Maybe the problem is caused by cheap cameras?
This could be the reason why some apps increase the screen brightness when displaying QR codes.

[Simon-Laux]

We could add https://github.com/dignifiedquire/quircs to core to easily make it accessible on android (without adding another native lib to the built process). as I told on the forum that library can scan the qr code in question with no problems. Maybe we can use both scanner libraries in tandem/parallel for better results?

Or on newer phones there could also be a google/android provided system library/sdk for scanning qr codes? the Chrome browser has one, so android might too?

[link2xt]

Maybe the problem is caused by cheap cameras?

If you see the QR code in camera and can reconstruct original one cell-by-cell in graphical editor, then QR code scanning software should be able to do it too. In practice it is much worse than that.

[iequidoo]

I think in the core it is transparent, because on Android background is white.

It's #f2f2f2 in the core and on Android too, i even checked it making a screenshot. So, almost white. I'd suggest to make it #ffffff however. And IDK why it's so gray in Desktop.

EDIT: As Simon-Laux noted below, it's really an optical illusion in Desktop light mode, the color is the same.

[Simon-Laux]

And IDK why it's so gray in Desktop.

It's the same in desktop, it is an optical illusion if you use desktop in light mode and android in dark mode or android background is not really white, I don't know, because I used android also in dark mode.

I suggest to solve the real problem which is the qr code scanner on android that is not good enough.
Please don't change the color before actually testing if it does anything, which I expect not, as the contrast is probably still high enough.
Solving the underlying problem of the bad scanner will also solve other issues, maybe it is because of the special perspective or the blurriness of the test image.

[Septias]

Maybe we should close this as we cannot reproduce the problem (Bjoern on ios and Simon with quircs were both able to decode the QR code just fine). Maybe the person in question has bad camera quality, too dim monitor or maybe it's the bad qr-code reading library from Android. It feels like there are too many moving pieces and it depends very much on every person, their settings, and their phone. I think it works well in general and these are only rare occasions.

[Septias]

It would be very easy to change the background btw:

deltachat-core-rust/src/qr_code_generator.rs

Line 135 in 29581c5

d.attr("style", "fill:#f2f2f2")?;