Dmitry VerkhoturovandUmputun
603decabf6
Telegram authentication requires you to open a chat on the phone. It's convenient to have a QR code for the case when you want to log in on the computer but have Telegram only on your phone and would be able to scan the QR instead of copy-pasting the link from the computer to the phone any other way. Originally we thought of generating QR on the client but found backend-generated QR a better alternative because we avoid adding one more JavaScript dependency to the frontend that way.
go-qrcode
Package qrcode implements a QR Code encoder. 
A QR Code is a matrix (two-dimensional) barcode. Arbitrary content may be encoded, with URLs being a popular choice :)
Each QR Code contains error recovery information to aid reading damaged or obscured codes. There are four levels of error recovery: Low, medium, high and highest. QR Codes with a higher recovery level are more robust to damage, at the cost of being physically larger.
Install
go get -u github.com/skip2/go-qrcode/...
A command-line tool qrcode will be built into $GOPATH/bin/.
Usage
import qrcode "github.com/skip2/go-qrcode"
-
Create a 256x256 PNG image:
var png []byte png, err := qrcode.Encode("https://example.org", qrcode.Medium, 256) -
Create a 256x256 PNG image and write to a file:
err := qrcode.WriteFile("https://example.org", qrcode.Medium, 256, "qr.png") -
Create a 256x256 PNG image with custom colors and write to file:
err := qrcode.WriteColorFile("https://example.org", qrcode.Medium, 256, color.Black, color.White, "qr.png")
All examples use the qrcode.Medium error Recovery Level and create a fixed 256x256px size QR Code. The last function creates a white on black instead of black on white QR Code.
Documentation
Demoapp
CLI
A command-line tool qrcode will be built into $GOPATH/bin/.
qrcode -- QR Code encoder in Go
https://github.com/skip2/go-qrcode
Flags:
-d disable QR Code border
-i invert black and white
-o string
out PNG file prefix, empty for stdout
-s int
image size (pixel) (default 256)
-t print as text-art on stdout
Usage:
1. Arguments except for flags are joined by " " and used to generate QR code.
Default output is STDOUT, pipe to imagemagick command "display" to display
on any X server.
qrcode hello word | display
2. Save to file if "display" not available:
qrcode "homepage: https://github.com/skip2/go-qrcode" > out.png
Maximum capacity
The maximum capacity of a QR Code varies according to the content encoded and the error recovery level. The maximum capacity is 2,953 bytes, 4,296 alphanumeric characters, 7,089 numeric digits, or a combination of these.
Borderless QR Codes
To aid QR Code reading software, QR codes have a built in whitespace border.
If you know what you're doing, and don't want a border, see https://gist.github.com/skip2/7e3d8a82f5317df9be437f8ec8ec0b7d for how to do it. It's still recommended you include a border manually.
Links
- http://en.wikipedia.org/wiki/QR_code
- ISO/IEC 18004:2006 - Main QR Code specification (approx CHF 198,00)
- https://github.com/qpliu/qrencode-go/ - alternative Go QR encoding library based on ZXing