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# go-qrcode #
<img src='https://skip.org/img/nyancat-youtube-qr.png' align='right'>
Package qrcode implements a QR Code encoder. [](https://travis-ci.org/skip2/go-qrcode)
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 `$GOPATH/bin/`.
## Usage
import qrcode "github.com/skip2/go-qrcode"
- **Create a PNG image:**
var png []byte
png, err := qrcode.Encode("https://example.org", qrcode.Medium, 256)
- **Create a PNG image and write to a file:**
err := qrcode.WriteFile("https://example.org", qrcode.Medium, 256, "qr.png")
- **Create a PNG image with custom colors and write to file:**
err := qrcode.WriteColorFile("https://example.org", qrcode.Medium, 256, color.Black, color.White, "qr.png")
All examples use the qrcode.Medium error Recovery Level and create a fixed
256x256px size QR Code. The last function creates a white on black instead of black
on white QR Code.
The maximum capacity of a QR Code varies according to the content encoded and
the error recovery level. The maximum capacity is 2,953 bytes, 4,296
alphanumeric characters, 7,089 numeric digits, or a combination of these.
## Documentation
[](https://godoc.org/github.com/skip2/go-qrcode)
## Demoapp
[http://go-qrcode.appspot.com](http://go-qrcode.appspot.com)
## CLI
A command-line tool `qrcode` will be built into `$GOPATH/bin/`.
```
qrcode -- QR Code encoder in Go
https://github.com/skip2/go-qrcode
Flags:
-o string
out PNG file prefix, empty for stdout
-s int
image size (pixel) (default 256)
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
```
## Links
- [http://en.wikipedia.org/wiki/QR_code](http://en.wikipedia.org/wiki/QR_code)
- [ISO/IEC 18004:2006](http://www.iso.org/iso/catalogue_detail.htm?csnumber=43655) - Main QR Code specification (approx CHF 198,00)<br>
- [https://github.com/qpliu/qrencode-go/](https://github.com/qpliu/qrencode-go/) - alternative Go QR encoding library based on [ZXing](https://github.com/zxing/zxing)
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