qrcode

README

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 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")
  

Both examples use the qrcode.Medium error Recovery Level and create a 256x256 pixel, 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

Demoapp

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
• 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

Documentation

Overview

Package qrcode implements a QR Code encoder.

A QR Code is a matrix (two-dimensional) barcode. Arbitrary content may be encoded.

A QR Code contains error recovery information to aid reading damaged or obscured codes. There are four levels of error recovery: qrcode.{Low, Medium, High, Highest}. QR Codes with a higher recovery level are more robust to damage, at the cost of being physically larger.

Two functions cover most use cases:

- 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")

Both examples use the qrcode.Medium error Recovery Level and create a 256x256 pixel, 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.

This package implements a subset of QR Code 2005, as defined in ISO/IEC 18004:2006.

Index

• func Encode(content string, level RecoveryLevel, size int) ([]byte, error)
• func EncodeWithFixPadding(content string, level RecoveryLevel, expectSize, padding int) ([]byte, error)
• func WriteFile(content string, level RecoveryLevel, size int, filename string) error
• type QRCode
  • func New(content string, level RecoveryLevel) (*QRCode, error)
  • func (q *QRCode) Bitmap() [][]bool
  • func (q *QRCode) Image(size int) image.Image
  • func (q *QRCode) Image2(expectSize, offset int) image.Image
  • func (q *QRCode) PNG(size int) ([]byte, error)
  • func (q *QRCode) PNG2(expectSize, padding int) ([]byte, error)
  • func (q *QRCode) Write(size int, out io.Writer) error
  • func (q *QRCode) WriteFile(size int, filename string) error
• type RecoveryLevel

Examples

• Encode
• WriteFile

Functions

func Encode

func Encode(content string, level RecoveryLevel, size int) ([]byte, error)

Encode a QR Code and return a raw PNG image.

size is both the image width and height in pixels. If size is too small then a larger image is silently returned.

To serve over HTTP, remember to send a Content-Type: image/png header.

Example

var png []byte
png, err := Encode("https://example.org", Medium, 256)

if err != nil {
	fmt.Printf("Error: %s", err.Error())
} else {
	fmt.Printf("PNG is %d bytes long", len(png))
}

func EncodeWithFixPadding

func EncodeWithFixPadding(content string, level RecoveryLevel, expectSize, padding int) ([]byte, error)

func WriteFile

func WriteFile(content string, level RecoveryLevel, size int, filename string) error

WriteFile encodes, then writes a QR Code to the given filename in PNG format.

size is both the width and height in pixels. If size is too small then a larger image is silently written.

Example

filename := "example.png"

err := WriteFile("https://example.org", Medium, 256, filename)

if err != nil {
	err = os.Remove(filename)
}

if err != nil {
	fmt.Printf("Error: %s", err.Error())
}

Types

type QRCode

type QRCode struct {
	// Original content encoded.
	Content string

	// QR Code type.
	Level         RecoveryLevel
	VersionNumber int

	// User settable drawing options.
	ForegroundColor color.Color
	BackgroundColor color.Color
	// contains filtered or unexported fields
}

A QRCode represents a valid encoded QRCode.

func New

func New(content string, level RecoveryLevel) (*QRCode, error)

New constructs a QRCode.

var q *qrcode.QRCode
q, err := qrcode.New("my content", qrcode.Medium)

An error occurs if the content is too long.

func (*QRCode) Bitmap

func (q *QRCode) Bitmap() [][]bool

Bitmap returns the QR Code as a 2D array of 1-bit pixels.

bitmap[y][x] is true if the pixel at (x, y) is set.

The bitmap includes the required "quiet zone" around the QR Code to aid decoding.

func (*QRCode) Image

func (q *QRCode) Image(size int) image.Image

Image returns the QR Code as an image.Image.

size is both the width and height in pixels.

func (*QRCode) Image2

func (q *QRCode) Image2(expectSize, offset int) image.Image

Image returns the QR Code as an image.Image.

size is both the width and height in pixels.

func (*QRCode) PNG

func (q *QRCode) PNG(size int) ([]byte, error)

PNG returns the QR Code as a PNG image.

size is both the image width and height in pixels. If size is too small then a larger image is silently returned.

func (*QRCode) PNG2

func (q *QRCode) PNG2(expectSize, padding int) ([]byte, error)

PNG returns the QR Code as a PNG image.

size is both the image width and height in pixels. If size is too small then a larger image is silently returned.

func (*QRCode) Write

func (q *QRCode) Write(size int, out io.Writer) error

Write writes the QR Code as a PNG image to io.Writer.

size is both the image width and height in pixels. If size is too small then a larger image is silently written.

func (*QRCode) WriteFile

func (q *QRCode) WriteFile(size int, filename string) error

WriteFile writes the QR Code as a PNG image to the specified file.

size is both the image width and height in pixels. If size is too small then a larger image is silently written.

type RecoveryLevel

type RecoveryLevel int

Error detection/recovery capacity.

There are several levels of error detection/recovery capacity. Higher levels of error recovery are able to correct more errors, with the trade-off of increased symbol size.

const (
	// Level L: 7% error recovery.
	Low RecoveryLevel = iota

	// Level M: 15% error recovery. Good default choice.
	Medium

	// Level Q: 25% error recovery.
	High

	// Level H: 30% error recovery.
	Highest
)