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87 lines
3.2 KiB
Markdown
87 lines
3.2 KiB
Markdown
# go-qrcode #
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<img src='https://skip.org/img/nyancat-youtube-qr.png' align='right'>
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Package qrcode implements a QR Code encoder. [](https://travis-ci.org/skip2/go-qrcode)
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A QR Code is a matrix (two-dimensional) barcode. Arbitrary content may be encoded, with URLs being a popular choice :)
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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.
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## Install
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go get -u github.com/skip2/go-qrcode/...
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A command-line tool `qrcode` will be built into `$GOPATH/bin/`.
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## Usage
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import qrcode "github.com/skip2/go-qrcode"
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- **Create a 256x256 PNG image:**
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var png []byte
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png, err := qrcode.Encode("https://example.org", qrcode.Medium, 256)
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- **Create a 256x256 PNG image and write to a file:**
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err := qrcode.WriteFile("https://example.org", qrcode.Medium, 256, "qr.png")
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- **Create a 256x256 PNG image with custom colors and write to file:**
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err := qrcode.WriteColorFile("https://example.org", qrcode.Medium, 256, color.Black, color.White, "qr.png")
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All examples use the qrcode.Medium error Recovery Level and create a fixed 256x256px size QR Code. The last function creates a white on black instead of black on white QR Code.
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## Documentation
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[](https://godoc.org/github.com/skip2/go-qrcode)
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## Demoapp
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[http://go-qrcode.appspot.com](http://go-qrcode.appspot.com)
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## CLI
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A command-line tool `qrcode` will be built into `$GOPATH/bin/`.
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```
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qrcode -- QR Code encoder in Go
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https://github.com/skip2/go-qrcode
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Flags:
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-d disable QR Code border
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-i invert black and white
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-o string
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out PNG file prefix, empty for stdout
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-s int
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image size (pixel) (default 256)
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-t print as text-art on stdout
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Usage:
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1. Arguments except for flags are joined by " " and used to generate QR code.
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Default output is STDOUT, pipe to imagemagick command "display" to display
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on any X server.
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qrcode hello word | display
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2. Save to file if "display" not available:
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qrcode "homepage: https://github.com/skip2/go-qrcode" > out.png
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```
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## Maximum capacity
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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.
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## Borderless QR Codes
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To aid QR Code reading software, QR codes have a built in whitespace border.
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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.
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## Links
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- [http://en.wikipedia.org/wiki/QR_code](http://en.wikipedia.org/wiki/QR_code)
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- [ISO/IEC 18004:2006](http://www.iso.org/iso/catalogue_detail.htm?csnumber=43655) - Main QR Code specification (approx CHF 198,00)<br>
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- [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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