@deltachat/react-qr-reader

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.
• In Firefox a prompt will be shown to the user asking which camera to use, so facingMode will not affect it.
• On IOS 11 it is only supported on Safari and not on Chrome or Firefox due to Apple making the API not available to 3th party browsers.

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: 300,
      result: "No result"
    };
    this.handleScan = this.handleScan.bind(this);
  }
  handleScan(data) {
    if (data) {
      this.setState({
        result: data
      });
    }
  }
  handleError(err) {
    console.error(err);
  }
  render() {
    return (
      <div>
        <QrReader
          delay={this.state.delay}
          onError={this.handleError}
          onScan={this.handleScan}
          style={{ width: "100%" }}
        />
        <p>{this.state.result}</p>
      </div>
    );
  }
}

Props

Events

Prop	Argument	Description
onScan	result	Scan event handler. Called every scan with the decoded value or null if no QR code was found.
onError	Error	Called when an error occurs.
onLoad	none	Called when the component is ready for use.
onImageLoad	img onLoad event	Called when the image in legacyMode is loaded.

Options

Prop	Type	Default	Description
delay	number or false	500	The delay between scans in milliseconds. To disable the interval pass in false.
facingMode	user or environment	environment	Specify which camera should be used (if available).
resolution	number	600	The resolution of the video (or image in legacyMode). Larger resolution will increase the accuracy but it will also slow down the processing time.
style	a valid React style	none	Styling for the container element. Warning The preview will always keep its 1:1 aspect ratio.
className	string	none	ClassName for the container element.
showViewFinder	boolean	true	Show or hide the build in view finder. See demo
constraints	object	null	Use custom camera constraints that the override default behavior. MediaTrackConstraints
legacyMode	boolean	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).

Dev

Install dependencies

npm install

Build

npm run build

Demo

npm run storybook

Linting

npm run lint

Tested platforms

• Chrome macOs & Android
• Firefox macOs & Android
• Safari macOs & IOS

License

The MIT License (MIT)

Copyright (c) 2018 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.