Reading QR codes without a computer
qr.blinry.org
Reading QR codes without a computer
1–10 of 93 posts
Re: Reading QR codes without a computer
#2Fun article
Re: Reading QR codes without a computer
#3I tried reading them manually about ten years ago, but gave up because of the mask. The mask pattern needs to be applied (xor) before you can even tell as much as the data type...
Does anyone know how much it actually helps QR code readers to have this mask pattern applied?
Last month, I tried to find out what the optimal error correction setting is (answer: none, if the matrix isn't damaged, like in my use-case where it's shown on a screen), which wasn't easy to find. I didn't find anyone who actually went out into the real world and tried out different settings and different scanning implementations to see what the effect is of choosing a good mask or choosing a good error correction value. In the end, a theoretical answer was enough for my application because I can assume the QRs to be pristine, but in a perfect world we also wouldn't need a mask setting. I then tried to do some research of my own by reading a small QR off my screen with different error correction levels and an intentionally shaking camera to simulate read issues when someone points a smartphone, but found no significant difference between any of the settings. With there being at least four alignment markers, a huge quiet area, and a "timing pattern", does it really matter if there are white blobs due to not having a mask?
(The secondary reason why I gave up trying to read QRs visually is because I noticed they always have the URL written below as fallback anyway. Since then, I did see a few times where there was no fallback, but it's very rare)
Re: Reading QR codes without a computer
#4I tried reading them manually about ten years ago, but gave up because of the mask. The mask pattern needs to be applied (xor) before you can even tell as much as the data type... Does anyone know how much it actually helps QR code readers to have this mask pattern applied? Last month, I tried to find out what the optimal error correction setting is (answer: none, if the matrix isn't damaged, like in my use-case wher…
The error correction is funny. If you don't use it, your message takes up less space, and the QR is smaller. If you have a fixed space to fit it in (e.g. printing to a sticker), that means your pixels can be physically bigger. For reliable reading, I found that physically bigger pixels helped more than the error correction itself.
Depending on the length of your message, sometimes you can turn up the error correction level without impacting the final QR dimensions, and in those cases it's a win/win.
Re: Reading QR codes without a computer
#5Slightly off topic: One day in the late 90s or early 2000s, I wanted to transfer the contents of my Atari 8-bit disks to my PC. I did know about SIO2PC, a cable that converts between Atari's SIO port and the PC's serial port and a piece of software to go with it. But I didn't have the electronics skills to build one (even though it is actually very easy).
So I ended up writing a Basic program on the Atari to read data from the disk sector by sector and paint it on the screen (with the large 4-color pixels of graphics mode 3). The Atari was connected to the TV card of my PC and a Delphi program I wrote was running on the PC that kept taking screen shots and trying to decode the data from there. I quickly learned that empty sectors threw off my pixel position calibration so I added a mask pattern and a checksum. The sector address was also included. With that, I was able to transfer all my disk contents to my PC. To this day I consider it my greatest engineering achievement :)
Some ten years later, I went on to build an SIO2PC program called AspeQt. A more up-to-date community fork called RespeQt is still the most popular tool in that category used by the community. It even has its own subforum on AtariAge[1].
[1] https://forums.atariage.com/forum/184-respeqt-sio2pc-softwar...
Re: Reading QR codes without a computer
#6Stupid 'trivia' question, but could someone generate the 'darkest' (most black pixels) and 'brightest (most white pixels) QR codes possible?
Re: Reading QR codes without a computer
#7Stupid 'trivia' question, but could someone generate the 'darkest' (most black pixels) and 'brightest (most white pixels) QR codes possible?
It’s of course possible, but the spec is trying to avoid this. There are multiple “masking patterns”, and the algorithm should choose one that gives fewest “penalty points”. Large single color areas are a lot of penalty points, so QR algorithm is trying to avoid them.
Re: Reading QR codes without a computer
#8Stupid 'trivia' question, but could someone generate the 'darkest' (most black pixels) and 'brightest (most white pixels) QR codes possible?
It’s of course possible, but the spec is trying to avoid this. There are multiple “masking patterns”, and the algorithm should choose one that gives fewest “penalty points”. Large single color areas are a lot of penalty points, so QR algorithm is trying to avoid them.
Yes - I think it would be interesting to see them actually produced. Could we get to 60% white pixels? Or 75%?
There could maybe be two solutions:
* Darkest/Brightest allowed by the QR algorithm,
* Darkest/Brightest technically valid, which would would not be chosen by the algorithm (i.e. if one manually chooses the masking pattern.
Perhaps also more solutions - 'Darkest/Brightest recognized by software X/Y/Z'
Re: Reading QR codes without a computer
#9> So is the rest all content? Not quite! There is also error correction, which is used to make sure that the QR code can still be read even if some parts are damaged, blurry, or missing. The error correction is generated by some fancy math, and we don't care about it here for the purpose of reading it by hand.
This should be explained better... I mean sure, the math can be hard.. but is the error correction appended at the end? After every byte? In the middle? Can we still read a qr code by hand if it has error correction (assuming it's not damaged, and we can skip the math part?)?
Re: Reading QR codes without a computer
#10I tried reading them manually about ten years ago, but gave up because of the mask. The mask pattern needs to be applied (xor) before you can even tell as much as the data type... Does anyone know how much it actually helps QR code readers to have this mask pattern applied? Last month, I tried to find out what the optimal error correction setting is (answer: none, if the matrix isn't damaged, like in my use-case wher…
Last year I did some experimentation along these lines and I also found that no error correction was best, at least when 3d printing QR codes. I was trying to find how small I could print it and still have it be detectable. Like the sibling comment, I suspect it is because of individually larger pixels.