Introduction

A React component for reading QR codes from the webcam. It uses the WebRTC standards for reading webcam data and jsQR is used for detecting QR codes in that data. To optimise the speed and experience, a web-worker is used to offload the heavy QR code algorithm on a separate process. The web worker is inlined and loaded on creation of the component.

Demo

thomasbilliet.com/react-qr-reader

Known Issues

• Due to browser implementations the camera can only be accessed over https or localhost.
• Not compatible with macOS/iOS Safari. Use legacyMode to support these platforms.
• In Firefox a prompt will be shown to the user asking which camera to use, so facingMode will not affect it.

Install

npm install --save react-qr-reader

Example

import React, { Component } from 'react'
import QrReader from 'react-qr-reader'

class Test extends Component {
  constructor(props){
    super(props)
    this.state = {
      delay: 100,
      result: 'No result',
    }

    this.handleScan = this.handleScan.bind(this)
  }
  handleScan(data){
    this.setState({
      result: data,
    })
  }
  handleError(err){
    console.error(err)
  }
  render(){
    const previewStyle = {
      height: 240,
      width: 320,
    }

    return(
      <div>
        <QrReader
          delay={this.state.delay}
          style={previewStyle}
          onError={this.handleError}
          onScan={this.handleScan}
          />
        <p>{this.state.result}</p>
      </div>
    )
  }
}

Props

onScan

Type: function, Required, Argument: result

Scan event handler. Called every scan with the decoded value or null if no QR code was found.

onError

Type: function, Required, Argument: error

Function to call when an error occurs such as:

• Not supported platform
• The lack of available devices

onLoad

Type: function, Optional

Called when the component is ready for use.

onImageLoad

Type: function, Optional, Argument: React img onLoad event

Called when the image in legacyMode is loaded.

delay

Type: number, Optional, Default: 500

The delay between scans in milliseconds. To disable the interval pass in false.

facingMode

Type: string, Optional

Specify which camera direction should be used (if available). Options: front and rear.

legacyMode

Type: boolean, Optional, Default: false.

If the device does not allow camera access (e.g. IOS Browsers, Safari) you can enable legacyMode to allow the user to take a picture (On a mobile device) or use an existing one. To trigger the image dialog just call the method openImageDialog from the parent component. Warning You must call the method from a user action (eg. click event on some element).

maxImageSize

Type: number, Optional, Default: 1500.

If legacyMode is active then the image will be downscaled to the given value while keepings its aspect ratio. Allowing larger images will increase the accuracy but it will also slow down the processing time.

style

Type: object, Optional

Styling for the preview element. This will be a video or an img when legacymode is true. Warning The preview will keep its aspect ratio, to disable this set the CSS property objectFit to fill.

className

Type: string, Optional

ClassName for the container element.

chooseDeviceId

Type: function, Optional, Arguments: (1) video devices matching facingMode, (2) all video devices

Called when choosing which device to use for scanning. By default chooses the first video device matching facingMode, if no devices match the first video device found is choosen.

Dev

Install dependencies

npm install

Build

npm run build

Demo

npm run storybook

Test

npm test

Linting

npm run lint

Tested platforms

• Chrome 56 and Firefox 53 on macOs 10.12
• Chrome 55 and Firefox 50 on Android 6.0.1

License

The MIT License (MIT)

Copyright (c) 2017 Thomas Billiet

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.