[Bounty offered] Fix QR flakiness

[za3k]

See: za3k/qr-backup#69 to collect the bounty. this is a cross-post.

there is exactly one widely-available command-line program in linux which reads QR codes, zbar. it has a problem -- it sometimes fails, even on digitally generated QR codes. the failure rate for digital codes should be 0%, because they have exactly all the right data.

at least 1/3 of bugs in the zbar issue tracker are about this. almost all of the bugs in the tracker are about QR codes.

fixing this problem will make qr-backup measurably better. it will also make QR reading better on linux in general, for a lot of people.

i suspect it will fix another 1/3 of the bugs in the zbar tracker, even though they are not explicitly about digitally-generated QR codes.

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zbar sometimes fails (>0.1% of the time) to scan a QR code. Fix this, changing the code of zbar to be correct, and get zbar to have a 0% error rate for digitally-generated images of QR codes.

Debugging tips:

• Set DEBUG_SVG and recompile
• Set QR_DEBUG, after merging the code in image.zip (source: Timothy Terriberry)

Reproduction case: https://user-images.githubusercontent.com/64830812/127732474-ff7fa13e-d913-4926-8361-ace8cf14d1f8.png

Code link: https://github.com/mchehab/zbar/tree/master/zbar/qrcode

Bounty: 10 hours of my time in trade