A Vue.js component, accessing the device camera and allowing users to read QR codes, within the browser.
No | Yes | Yes | Yes | 11+ |
- Chrome requires HTTPS or localhost.
- on iOS, it doesn't (yet?) work in non-Safari browsers (see #29)
- more details on Caniuse
Once a stream from the users camera is loaded, it is displayed and continuously scanned for QR codes. Results are indicated by the decode
event.
<qrcode-reader @decode="onDecode"></qrcode-reader>
methods: {
onDecode (decodedString) {
// ...
}
}
It might take a while before the component is ready and the scanning process starts. The user has to be asked for camera access permission first and the camera stream has to be loaded.
If you want to show a loading indicator, you can listen for the init
event. It's emitted as soon as the component is mounted and carries a promise which resolves when everything is ready. The promise is rejected if initialization fails. This can have a couple of reasons.
👉 In Chrome you can't prompt users for permissions a second time. Once denied, users can only manually grant them. Make sure your users understand why you need access to their camera before you mount this component. Otherwise they might panic and deny and then get frustrated because they don't know how to change their decision.
<qrcode-reader @init="onInit"></qrcode-reader>
methods: {
async onInit (promise) {
// show loading indicator
try {
await promise
// successfully initialized
} catch (error) {
if (error.name === 'NotAllowedError') {
// user denied camera access permisson
} else if (error.name === 'NotFoundError') {
// no suitable camera device installed
} else if (error.name === 'NotSupportedError') {
// page is not served over HTTPS (or localhost)
} else if (error.name === 'NotReadableError') {
// maybe camera is already in use
} else if (error.name === 'OverconstrainedError') {
// passed constraints don't match any camera. Did you requested the front camera although there is none?
} else {
// browser is probably lacking features (WebRTC, Canvas)
}
} finally {
// hide loading indicator
}
}
}
By default detected QR codes are visually highlighted. A transparent canvas overlays the camera stream. When a QR code is detected, its location is painted to the canvas. You can enable/disable this feature by passing true
/false
via the track
prop. If tracking is disabled the camera stream is scanned much less frequently. So if you encounter performance problems on your target device, this might help.
You can also pass a function with track
to customize the way the location is painted. This function is called to produce each frame. It receives the location object as the first argument and a CanvasRenderingContext2D
instance as the second argument.
👉 Avoid access to reactive properties in this function (like stuff in data
, computed
or your Vuex store). The function is called several times a second and might cause memory leaks. If you want to be save don't access this
at all.
Say you want to paint in a different color that better fits your overall page theme.
<qrcode-reader :track="repaintLocation"></qrcode-reader>
methods: {
repaintLocation (location, ctx) {
if (location !== null) {
const {
topLeftCorner,
topRightCorner,
bottomLeftCorner,
bottomRightCorner,
} = location
ctx.strokeStyle = 'blue' // instead of red
ctx.beginPath()
ctx.moveTo(topLeftCorner.x, topLeftCorner.y)
ctx.lineTo(bottomLeftCorner.x, bottomLeftCorner.y)
ctx.lineTo(bottomRightCorner.x, bottomRightCorner.y)
ctx.lineTo(topRightCorner.x, topRightCorner.y)
ctx.lineTo(topLeftCorner.x, topLeftCorner.y)
ctx.closePath()
ctx.stroke()
}
}
}
Distributed content will overlay the camera stream, wrapped in a position: absolute
container.
<qrcode-reader>
<b>stuff here overlays the camera stream</b>
</qrcode-reader>
With the paused
prop you can prevent further decode
propagation and functions passed via track
are stopped being called. Useful for example if you're only interested in the first result. This will also freeze the camera stream.
<qrcode-reader @decode="onDecode" :paused="paused"></qrcode-reader>
data () {
return {
paused: false
}
},
methods: {
onDecode (content) {
this.paused = true
// ...
}
}
This component uses getUserMedia to request camera streams. This method accepts a constraints object to configure for example if front or rear camera should be accessed. This is passed by default:
{
audio: false, // don't request microphone access
video: {
facingMode: { ideal: 'environment' }, // use rear camera if available
width: { min: 360, ideal: 680, max: 1920 }, // constrain video width resolution
height: { min: 240, ideal: 480, max: 1080 }, // constrain video height resolution
frameRate: { min: 10, ideal: 25 }
}
}
You can change the video
part using the video-constraints
prop. Note that you only have to pass properties you want to override. If you want to use the front camera for example and change nothing else, pass this:
<qrcode-reader :video-constraints="{ facingMode: 'user' }"></qrcode-reader>
👉 If you change this property after initialization, a new camera stream will be requested and the init
event will be emitted again.
yarn add vue-qrcode-reader
or using NPM:
npm install --save vue-qrcode-reader
Register component globally:
import Vue from 'vue'
import VueQrcodeReader from 'vue-qrcode-reader'
Vue.use(VueQrcodeReader)
Register locally in other components scope:
import Vue from 'vue'
import { QrcodeReader } from 'vue-qrcode-reader'
Vue.component('my-component', {
components: { QrcodeReader },
// ...
)
Register component globally:
import 'vue-qrcode-reader/dist/vue-qrcode-reader.css'
import VueQrcodeReader from 'vue-qrcode-reader/dist/vue-qrcode-reader.common'
Vue.use(VueQrcodeReader)
Register locally in other components scope:
import 'vue-qrcode-reader/dist/vue-qrcode-reader.css'
import { QrcodeReader } from 'vue-qrcode-reader/dist/vue-qrcode-reader.common'
Vue.component('my-component', {
components: { QrcodeReader },
// ...
)
<link rel="stylesheet" href="vue-qrcode-reader/dist/vue-qrcode-reader.css"/>
<script src="vue.js"></script>
<script src="vue-qrcode-reader/dist/vue-qrcode-reader.browser.js"></script>
The plugin should be auto-installed. If not, you can install it manually with the instructions below.
Register component globally:
Vue.use(VueQrcodeReader)
Register locally in other components scope:
Vue.component('my-component', {
components: {
'qrcode-reader': VueQrcodeReader.QrcodeReader
},
// ...
)
Register component globally:
import Vue from 'vue'
import VueQrcodeReader from 'vue-qrcode-reader/src'
Vue.use(VueQrcodeReader)
Register locally in other components scope:
import Vue from 'vue'
import { QrcodeReader } from 'vue-qrcode-reader/src'
Vue.component('my-component', {
components: { QrcodeReader },
// ...
)
.vue
files. More info in the official documentation.