I would love a game where you learn to actually read QR codes by eyesight - and quickly. Would be quite fun to have an impressive and not very useful skill
Reading QR codes without a computer
61–70 of 93 posts
Re: Reading QR codes without a computer
#62I would love a game where you learn to actually read QR codes by eyesight - and quickly. Would be quite fun to have an impressive and not very useful skill
Not sure if it's possible to be honest, it might be if you can sit down with a pen a paper. But again we've seen human perform seemingly impossible tasks before, so who knows.
Re: Reading QR codes without a computer
#63I 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…
Physically bigger pixels help a lot indeed. The encoding mode also helps make pixels bigger.
This is very convenient when you control the QR reader and need to represent long numeric identifiers like UUIDs.
For example:
9728983f-7d7d-4189-b624-f92781e36650 (lowercase UUID):
=> length=36, 15 pixels between markers
JWM9GFVXFN0RKDH4Z4KR3RV6A0 (base32 UUID):
=> length=26, 11 pixels between markers
9728983F-7D7D-4189-B624-F92781E36650 (uppercase UUID):
=> length=36, 11 pixels between markers
200924207194334734815443970355691218512 (decimal UUID):
=> length=39, 7 pixels between markers
The decimal UUID is a longer string, but results in much bigger pixels because it can use numeric encoding.
I have a QR code base attendance tracker [1], where attendees show the code [2] on their phones (glares, etc.), in bad lighting conditions, etc. Bigger pixels means scanning stays quick. Same with parcel tracking [3] where field agents might need to scan QR codes in barely-lit hallways, etc.
[1] https://workspace.google.com/marketplace/app/qr_code_pass_fo...
Re: Reading QR codes without a computer
#64Semi-related, there was a recent puzzle (part of an offshoot of the 2023 Mystery Hunt), which required you to decipher a really broken QR code by hand (too far for error correction to work). We ended up looking at all the guides listed in this comment section, and while they were useful, none were super great. It's always nice to have more detailed articles like this, and this one definitely seems very polished!
Here's the puzzle for anyone curious, though the QR code deciphering comes in the 2nd half: https://puzzles.mit.edu/2023/abcde.puzzlefactory.place/puzzl...
Re: Reading QR codes without a computer
#65Looking on Wikipedia I see that QR code was invented in 1994 by a Japanese automotive components manufacturer to label car parts. I wonder if QR code was invented today, could it be improved? Maybe for compactness? Ease of read?
they would be hexagons
Re: Reading QR codes without a computer
#66> 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…
An Artisanal QR Code [1] shows how to compute the checksum by hand using arithmetic similar to a long division. There are actually two slightly different codes (Reed-Solomon and BCH) for different pieces of information.
Re: Reading QR codes without a computer
#67Looking on Wikipedia I see that QR code was invented in 1994 by a Japanese automotive components manufacturer to label car parts. I wonder if QR code was invented today, could it be improved? Maybe for compactness? Ease of read?
There's nothing stopping a new sufficiently better design. Bar codes were already ubiquitous in 94 and they didn't prevent QR codes taking off.
Maybe there's not that much left to improve. (unless changing the concept drastically, e.g. NFC)
Re: Reading QR codes without a computer
#68Earlier quoted context omitted.
Barcodes use the last digit as a checksum. The checksum is some adding up the numbers and multiplying or something, then % 10 (only 0-9 possible values). As you can see with this math, the error checking has a 1/10 of a chance of coincidentally showing a correct checksum in cases where the data is incorrect. Either way, that last digit on barcodes is insignificant to the actual product's unique barcode ID. Fun story:…
When I worked at a grocery store in the 2000s, you didn't need the checksum digit when keying in a barcode by hand. In fact, manually entering the checksum digit would result in a "product not found" error. So I wonder if the checker had to manually look anything up, assuming it was only the checksum digit that was frayed off. Perhaps some POS systems do require the checksum digit for manually-entered barcodes, thoug…
>In fact, manually entering the checksum digit would result in a "product not found" error.
That is hilarious to me. The obviously safer approach of checking the check digit was not merely neglected, but actively forbidden.
Re: Reading QR codes without a computer
#69You’ve got to watch out reading those QR codes with your mind as you might contract a lethal mind-virus!
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Re: Reading QR codes without a computer
#70I would love a game where you learn to actually read QR codes by eyesight - and quickly. Would be quite fun to have an impressive and not very useful skill
Not sure if it's possible to be honest, it might be if you can sit down with a pen a paper. But again we've seen human perform seemingly impossible tasks before, so who knows.
I've always wanted to see someone encode/decode Base64 in their head.
At best, I've learned to recognize a base64 string that begins with "eyJ" is likely JSON.
Also, if you asked me what the base64 encoding of "password" is, but if you showed me "cGFzc3dvcmQ=" and asked me what the decoded value is, I'd recognize it as "password". Though you could probably change a few digits and fool me.