# go-qrcode # <img src='https://skip.org/img/nyancat-youtube-qr.png' align='right'> Package qrcode implements a QR Code encoder. [![Build Status](https://travis-ci.org/skip2/go-qrcode.svg?branch=master)](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 `$GOPATH/bin/`. ## Usage import qrcode "github.com/skip2/go-qrcode" - **Create a PNG image:** var png []byte png, err := qrcode.Encode("https://example.org", qrcode.Medium, 256) - **Create a PNG image and write to a file:** err := qrcode.WriteFile("https://example.org", qrcode.Medium, 256, "qr.png") - **Create a PNG image with custom colors and write to file:** err := qrcode.WriteColorFile("https://example.org", qrcode.Medium, 256, color.Black, color.White, "qr.png") All examples use the qrcode.Medium error Recovery Level and create a fixed 256x256px size QR Code. The last function creates a white on black instead of black on white QR Code. The maximum capacity of a QR Code varies according to the content encoded and the error recovery level. The maximum capacity is 2,953 bytes, 4,296 alphanumeric characters, 7,089 numeric digits, or a combination of these. ## Documentation [![godoc](https://godoc.org/github.com/skip2/go-qrcode?status.png)](https://godoc.org/github.com/skip2/go-qrcode) ## Demoapp [http://go-qrcode.appspot.com](http://go-qrcode.appspot.com) ## CLI A command-line tool `qrcode` will be built into `$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)