Re:Encoding your WiFi access point password into a QR code
by jlgaddis on Sunday December 29, 2019 @02:31PM
(#21907908)
Seems like the obvious thing would be to have the QR code contain a "receipt ID" (UUID?) in a URL.
When the QR code is scanned, the browser opens to the URL, the remote side takes your "receipt ID", and presents you with a list of all the items you purchased.
I can't imagine any decent-sized retailer isn't already maintaining records like this.
Re:Encoding your WiFi access point password into a QR code
by naniwaduni on Sunday December 29, 2019 @05:21PM
(#21908993)
See, one of the useful properties of a paper receipt is that, once you receive it, you can be fairly confident about the ~one way you're going to lose it
Re:Encoding your WiFi access point password into a QR code
by jmiserez on Monday December 30, 2019 @10:32AM
(#21913951)
Two ways. Receipts fade, sometimes very quickly.
Re:Encoding your WiFi access point password into a QR code
by tzs on Sunday December 29, 2019 @11:08PM
(#21910741)
1.2 kilobytes = 9.6 kilobits. If you need 61 bits per line, you’ve got enough bits for 157 lines. 393 lines if we go with 3 kilobytes. I think you may have used 61 bytes per line in your calculation rather than 61 bits.
Re:Encoding your WiFi access point password into a QR code
by colejohnson66 on Monday December 30, 2019 @11:48PM
(#21919028)
I (not OP) would say bytes would be closer. The product name could be 20 characters long (20 bytes minimum)
Re:Encoding your WiFi access point password into a QR code
by tzs on Tuesday December 31, 2019 @01:51AM
(#21919422)
OP was assuming the receipt would list the product UPC code rather than product name. A UPC code is 12 digits, which can be encoded in 40 bits.
Re:Encoding your WiFi access point password into a QR code
by smegger001 on Sunday December 29, 2019 @12:16PM
(#21907040)
it could just contain a url linking to a page with to content.
My back-of-the-envelope calculations say you'd need 61 bits per line on a receipt just to encode UPC, quantity and price. So the largest QR code would only allow 19-50 lines. And that's without including data like the store name, special offers, means of payment and so on. Believe me, plenty of people buy more than 50 items in their supermarket christmas shop :)
Standardised digital receipts would be neat but, QR codes encoding the data ain't the way to go about it.
[1] https://www.qrcode.com/en/about/version.html [2] https://commons.wikimedia.org/wiki/File:Qr-code-ver-40.svg