[HN Gopher] Creating a QR Code step by step
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Creating a QR Code step by step
Author : creolabs
Score : 262 points
Date : 2020-08-11 11:10 UTC (11 hours ago)
(HTM) web link (www.nayuki.io)
(TXT) w3m dump (www.nayuki.io)
| dontbenebby wrote:
| Along similar lines is there any guides on making more artful QR
| codes? I've seen ones that aren't square but still scan and found
| them fascinating.
| russellbeattie wrote:
| Though QR codes are very interesting technically, they were
| designed to be used by devices with orders of magnitude less
| computational power than is currently the norm, and much lower
| resolution optics as well. This is a good thing from an error-
| prevention perspective, but I wonder if a more modern QR code
| could be designed for today's smartphones.
|
| I think an interesting new standard would take advantage of
| higher resolution cameras and OCR functionality to make data
| transparent to the consumer. I personally wonder what the hell is
| going to pop up on my phone every time I use a QR code... Text?
| URL? Link to an app store? Who knows. A standard which marks text
| as "data" would let a user know what they're saving, and let them
| point a camera in the general direction of some text, and all the
| relevant info be extracted and organized. (Think addresses,
| receipts, etc.) I already use my phone to remember lots of things
| - like I take a picture of the back of my DSL router for the
| access codes printed there, or take a picture of my bike tire to
| remember the size of the tube I need, etc.
|
| Or if transparency isn't important, given we have 4K cameras now,
| imagine if there was a popular standard using steganography! I
| can imagine movie posters having showtimes, director and actor
| info, URLs for streaming it online, etc. all baked into the
| image.
| Bokanovsky wrote:
| For those interested in the creation of the QR code. Japanese TV
| Station NHK World have a 15 minute documentary charting it's
| creation -
| https://www3.nhk.or.jp/nhkworld/en/ondemand/video/2072031/
|
| It also features interesting details such as how they figured out
| the ratio of the marker squares should be.
| layoutIfNeeded wrote:
| >The math behind computing the Reed-Solomon error correction
| codes is omitted because it is long, tedious, and not very
| interesting.
|
| LOL! That's probably the most difficult part of creating a QR
| code, the rest is just framing/padding the data which is pretty
| obvious.
| mytailorisrich wrote:
| I'd argue that while Reed-Solomon is used in QR codes, the math
| behind it is not central to explaining how to create a QR code,
| and there are plenty of material available on Reed-Solomon.
|
| Specific framing/padding of the data is what makes a QR code.
| This may be simpler than explaining how Reed-Solomon codes work
| but it is not obvious.
|
| I think it is good that this article stays on point.
| nayuki wrote:
| Other discussions on Hacker News and Reddit have requested me
| to show the Reed-Solomon ECC calculations too (see
| https://news.ycombinator.com/item?id=18370829 ).
|
| mytailorisrich is correct; Reed-Solomon is used by many
| different standards, so it's not difficult if you learned it
| elsewhere. Whereas other parts of the QR Code standard are
| idiosyncratic, i.e. unique to it. If you want to see for
| yourself, go learn how Data Matrix works (another 2D barcode)
| and notice how little knowledge you can carry between the two
| standards.
|
| As for showing the Reed-Solomon calculations, I stand by my
| statement of them being long and tedious. Moreover, it
| requires background knowledge of finite field arithmetic (as
| opposed to ordinary arithmetic), which increases the
| explanation length and makes the calculations even more
| difficult to follow by hand.
|
| The actual Reed-Solomon encoding is conceptually simple.
| First you choose a generator element. Then you create a
| divisor polynomial by multiplying monomial terms involving
| powers of the generator. Then you encode the message as a
| polynomial, and finally divide the message by the divisor to
| yield the remainder polynomial, which is the final RS ECC
| data.
|
| If you want to see the cryptic verbosity of tons of numbers,
| here are examples: https://www.backblaze.com/blog/reed-
| solomon/ ; https://www.youtube.com/watch?v=H2LlHOw_ANg (AES)
| jedimastert wrote:
| For those curious, I've always found Computerphile has a
| reasonable explanation for most things
|
| https://www.youtube.com/watch?v=fBRMaEAFLE0
| eru wrote:
| And perhaps the most interesting part, too.
| rsync wrote:
| ... or you could just use an "Oh By" code.[1]
|
| No app, no reader, and you can just chalk/write/scratch it
| anywhere you like.
|
| This message, for instance, is at: 0xH6VYP7 [2]
|
| [1] https://0x.co/
|
| [2] https://0x.co/H6VYP7
| nayuki wrote:
| What happens when the company goes out of business?
|
| What happens when you try requesting random short URLs to peep
| on other people's texts?
| rsync wrote:
| "What happens when you try requesting random short URLs to
| peep on other people's texts?"
|
| I think most use-cases involve a code that you chalk up, or
| write, or paste publicly ... I am not sure that the codes
| being secret will be a common use-case.
|
| There's a fair amount of space in a 6-digit alpha-numeric
| code, though (36^6, roughly) ... that's a lot of brute
| forcing ...
| nayuki wrote:
| 36^6 = 2,176,782,336
| rsync wrote:
| Correct - thank you.
| rsync wrote:
| "What happens when the company goes out of business?"
|
| That's the most frequently asked question.
|
| rsync.net has been providing service, continuously, for 19
| years, so it's not without a good track record that I say I
| will keep "Oh By" running forever, even if it doesn't make
| any money.
|
| Interesting trivia: Oh By has actually made money ... as in,
| people have paid for custom Oh By codes.
| anamexis wrote:
| I get an SSL error NET::ERR_CERT_COMMON_NAME_INVALID, with the
| certificate's subject being dock.shp.mcafee.com
|
| Edit: Never mind, it's my ISP (CenturyLink) being dumb and
| saying it's malicious. Need to figure out how to disable that.
| bartvk wrote:
| Previous discussion:
| https://news.ycombinator.com/item?id=18360847
| asutekku wrote:
| I appreciate the steps, but this fails to answer a question
| which, imho, is way too often omitted in tech tutorials, and
| that's "Why?".
|
| Sure, I understand these are just the steps to create a QR code
| and I could just Google why the QR code needs a masking pattern,
| but that's besides the point. A good material would explain why I
| need it, instead of just saying it should be done. Even one
| sentence would be sufficient.
| Slartie wrote:
| The utility of the masking pattern becomes clear when following
| the next steps, which calculate "penalty points" for dot
| patterns in the QR code that might occur naturally, but are
| known to make it harder to read and more prone to erroneous
| reads. The masking pattern that, when applied to the "clean"
| content, generates the least problematic output is chosen.
|
| I found this pretty self-explanatory while just following the
| individual steps. However, a few sentences detailing the
| higher-level algorithm and its purpose right before the step
| which first introduces the masking pattern probably wouldn't be
| a bad idea either.
| patrickg wrote:
| I have written a QR encoder in Lua and documented it a bit.
| Perhaps this goes into the direction?
|
| http://speedata.github.io/luaqrcode/docs/qrencode.html
| nayuki wrote:
| I agree that the why is important, and it reinforces
| understanding of the how. I share your frustration when I see
| technical tutorials that show a bunch of screenshots or make
| you type a bunch of command line actions without explaining
| what it does and why you should do it.
|
| In this case though, I chose to omit the why because other
| written resources on QR Codes have covered the topics
| extensively. Just to name a few:
| https://en.wikipedia.org/wiki/QR_code ;
| http://datagenetics.com/blog/november12013/index.html ;
| https://en.wikipedia.org/wiki/Error_correction_code#Interlea...
| ; https://en.wikipedia.org/wiki/Clock_recovery
| amenghra wrote:
| An artisanal QR code goes over the error correcting code by
| manually calculating the long division:
| https://www.quaxio.com/an_artisanal_qr_code.html
| mare5x wrote:
| This is a great resource. I used it along with another practical
| tutorial (https://www.thonky.com/qr-code-tutorial/) to complement
| the official QR code standard when I wrote my own QR code encoder
| in Common Lisp: https://github.com/mare5x/LispQR
| jrexilius wrote:
| This was a good exploration of your approach. The interactive
| usage inline with description was very helpful. As some have
| pointed out, some expansion in certain areas could improve it,
| but still good.
|
| As a side note, I'm looking into using your libraries. They do
| seem fairly solid and efficient.
|
| Thanks for putting this out there!
| ChrisMarshallNY wrote:
| That's really cool! Thanks for sharing it!
| NilsIRL wrote:
| I found this video to be a lot clearer and with the combination
| of the website makes understanding easier:
| https://www.youtube.com/watch?v=KA8hDldvfv0
| katsume3 wrote:
| How small can you make a QR code until it can't be scanned by a
| phone?
| flixic wrote:
| During quarantine I designed a paper-based system for making QR
| codes by hand. Everything is very papery and bureaucratic, but
| also fun. Tables to look up bytes, long forms for calculating
| Reed-Solomon, and even transparent sheets of paper for comparing
| different masking patterns.
|
| My goal is to film a video of generating a QR code without any
| computers or even calculators. It's possible, just might take two
| hours or so.
| dang wrote:
| Please post it to HN when it's ready, and let us know at
| hn@ycombinator.com.
| latchkey wrote:
| That's awesome. Reminds me of Ken Shirriff computing sha256
| with pencil and paper...
|
| http://www.righto.com/2014/09/mining-bitcoin-with-pencil-and...
| flixic wrote:
| This was the main inspiration! Also, the fact that I couldn't
| find anyone going through EVERY step of QR code generation
| manually (even if CPU-assisted) and in detail.
| IanCal wrote:
| It's a great way to learn. In my cryptography classes we did
| all of the algorithms by hand (often shortened, so 16 rounds
| of something would be dropped to 3 or min bytes dropped) on
| pen and paper as homework. Hard but it really did make a lot
| stick in my mind about how things worked.
| MrZander wrote:
| I'd be very interested in seeing this when you are done!
| AimForTheBushes wrote:
| This sounds pretty cool. Hope you share it when it's finished!
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(page generated 2020-08-11 23:01 UTC)