add method for checking whether device has a camera

demo/index.html

@@ -22,6 +22,9 @@
 </style>
 <h1>Scan from WebCam:</h1>
 <div>
+    <b>Device has camera: </b>
+    <span id="cam-has-camera"></span>
+    <br>
     <video muted playsinline id="qr-video"></video>
     <canvas id="debug-canvas"></canvas>
 </div>
@@ -50,6 +53,7 @@
     const debugCheckbox = document.getElementById('debug-checkbox');
     const debugCanvas = document.getElementById('debug-canvas');
     const debugCanvasContext = debugCanvas.getContext('2d');
+    const camHasCamera = document.getElementById('cam-has-camera');
     const camQrResult = document.getElementById('cam-qr-result');
     const fileSelector = document.getElementById('file-selector');
     const fileQrResult = document.getElementById('file-qr-result');
@@ -63,6 +67,8 @@
 
     // ####### Web Cam Scanning #######
 
+    QrScanner.hasCamera().then(hasCamera => camHasCamera.textContent = hasCamera);
+
     const scanner = new QrScanner(video, result => setResult(camQrResult, result));
     scanner.start();
 

qr-scanner.min.js

@@ -1,18 +1,19 @@
 /*
  @asset(/libraries/qr-scanner/qr-scanner-worker.min.js) */
-'use strict';export default class QrScanner{constructor(video,onDecode,canvasSize=QrScanner.DEFAULT_CANVAS_SIZE){this.$video=video;this.$canvas=document.createElement("canvas");this._onDecode=onDecode;this._active=false;this._paused=false;this.$canvas.width=canvasSize;this.$canvas.height=canvasSize;this._sourceRect={x:0,y:0,width:canvasSize,height:canvasSize};this._onCanPlay=this._onCanPlay.bind(this);this._onPlay=this._onPlay.bind(this);this._onVisibilityChange=this._onVisibilityChange.bind(this);
-this.$video.addEventListener("canplay",this._onCanPlay);this.$video.addEventListener("play",this._onPlay);document.addEventListener("visibilitychange",this._onVisibilityChange);this._qrWorker=new Worker(QrScanner.WORKER_PATH)}destroy(){this.$video.removeEventListener("canplay",this._onCanPlay);this.$video.removeEventListener("play",this._onPlay);document.removeEventListener("visibilitychange",this._onVisibilityChange);this.stop();this._qrWorker.postMessage({type:"close"})}start(){if(this._active&&
-!this._paused)return Promise.resolve();if(window.location.protocol!=="https:")console.warn("The camera stream is only accessible if the page is transferred via https.");this._active=true;this._paused=false;if(document.hidden)return Promise.resolve();clearTimeout(this._offTimeout);this._offTimeout=null;if(this.$video.srcObject){this.$video.play();return Promise.resolve()}let facingMode="environment";return this._getCameraStream("environment",true).catch(()=>{facingMode="user";return this._getCameraStream()}).then((stream)=>
-{this.$video.srcObject=stream;this._setVideoMirror(facingMode)}).catch((e)=>{this._active=false;throw e;})}stop(){this.pause();this._active=false}pause(){this._paused=true;if(!this._active)return;this.$video.pause();if(this._offTimeout)return;this._offTimeout=setTimeout(()=>{const track=this.$video.srcObject&&this.$video.srcObject.getTracks()[0];if(!track)return;track.stop();this.$video.srcObject=null;this._offTimeout=null},300)}static scanImage(imageOrFileOrUrl,sourceRect=null,worker=null,canvas=
-null,fixedCanvasSize=false,alsoTryWithoutSourceRect=false){const promise=new Promise((resolve,reject)=>{if(!worker){worker=new Worker(QrScanner.WORKER_PATH);worker.postMessage({type:"inversionMode",data:"both"})}let timeout,onMessage,onError;onMessage=(event)=>{if(event.data.type!=="qrResult")return;worker.removeEventListener("message",onMessage);worker.removeEventListener("error",onError);clearTimeout(timeout);if(event.data.data!==null)resolve(event.data.data);else reject("QR code not found.")};
-onError=(e)=>{worker.removeEventListener("message",onMessage);worker.removeEventListener("error",onError);clearTimeout(timeout);var errorMessage=!e?"Unknown Error":e.message||e;reject("Scanner error: "+errorMessage)};worker.addEventListener("message",onMessage);worker.addEventListener("error",onError);timeout=setTimeout(()=>onError("timeout"),3E3);QrScanner._loadImage(imageOrFileOrUrl).then((image)=>{const imageData=QrScanner._getImageData(image,sourceRect,canvas,fixedCanvasSize);worker.postMessage({type:"decode",
-data:imageData},[imageData.data.buffer])}).catch(reject)});if(sourceRect&&alsoTryWithoutSourceRect)return promise.catch(()=>QrScanner.scanImage(imageOrFileOrUrl,null,worker,canvas,fixedCanvasSize));else return promise}setGrayscaleWeights(red,green,blue){this._qrWorker.postMessage({type:"grayscaleWeights",data:{red,green,blue}})}setInversionMode(inversionMode){this._qrWorker.postMessage({type:"inversionMode",data:inversionMode})}_onCanPlay(){this._updateSourceRect();this.$video.play()}_onPlay(){this._updateSourceRect();
-this._scanFrame()}_onVisibilityChange(){if(document.hidden)this.pause();else if(this._active)this.start()}_updateSourceRect(){const smallestDimension=Math.min(this.$video.videoWidth,this.$video.videoHeight);const sourceRectSize=Math.round(2/3*smallestDimension);this._sourceRect.width=this._sourceRect.height=sourceRectSize;this._sourceRect.x=(this.$video.videoWidth-sourceRectSize)/2;this._sourceRect.y=(this.$video.videoHeight-sourceRectSize)/2}_scanFrame(){if(!this._active||this.$video.paused||this.$video.ended)return false;
-requestAnimationFrame(()=>{QrScanner.scanImage(this.$video,this._sourceRect,this._qrWorker,this.$canvas,true).then(this._onDecode,(error)=>{if(this._active&&error!=="QR code not found.")console.error(error)}).then(()=>this._scanFrame())})}_getCameraStream(facingMode,exact=false){const constraintsToTry=[{width:{min:1024}},{width:{min:768}},{}];if(facingMode){if(exact)facingMode={exact:facingMode};constraintsToTry.forEach((constraint)=>constraint.facingMode=facingMode)}return this._getMatchingCameraStream(constraintsToTry)}_getMatchingCameraStream(constraintsToTry){if(constraintsToTry.length===
-0)return Promise.reject("Camera not found.");return navigator.mediaDevices.getUserMedia({video:constraintsToTry.shift()}).catch(()=>this._getMatchingCameraStream(constraintsToTry))}_setVideoMirror(facingMode){const scaleFactor=facingMode==="user"?-1:1;this.$video.style.transform="scaleX("+scaleFactor+")"}static _getImageData(image,sourceRect=null,canvas=null,fixedCanvasSize=false){canvas=canvas||document.createElement("canvas");const sourceRectX=sourceRect&&sourceRect.x?sourceRect.x:0;const sourceRectY=
-sourceRect&&sourceRect.y?sourceRect.y:0;const sourceRectWidth=sourceRect&&sourceRect.width?sourceRect.width:image.width||image.videoWidth;const sourceRectHeight=sourceRect&&sourceRect.height?sourceRect.height:image.height||image.videoHeight;if(!fixedCanvasSize&&(canvas.width!==sourceRectWidth||canvas.height!==sourceRectHeight)){canvas.width=sourceRectWidth;canvas.height=sourceRectHeight}const context=canvas.getContext("2d",{alpha:false});context.imageSmoothingEnabled=false;context.drawImage(image,
-sourceRectX,sourceRectY,sourceRectWidth,sourceRectHeight,0,0,canvas.width,canvas.height);return context.getImageData(0,0,canvas.width,canvas.height)}static _loadImage(imageOrFileOrUrl){if(imageOrFileOrUrl instanceof HTMLCanvasElement||imageOrFileOrUrl instanceof HTMLVideoElement||window.ImageBitmap&&imageOrFileOrUrl instanceof window.ImageBitmap||window.OffscreenCanvas&&imageOrFileOrUrl instanceof window.OffscreenCanvas)return Promise.resolve(imageOrFileOrUrl);else if(imageOrFileOrUrl instanceof Image)return QrScanner._awaitImageLoad(imageOrFileOrUrl).then(()=>
-imageOrFileOrUrl);else if(imageOrFileOrUrl instanceof File||imageOrFileOrUrl instanceof URL||typeof imageOrFileOrUrl==="string"){const image=new Image;if(imageOrFileOrUrl instanceof File)image.src=URL.createObjectURL(imageOrFileOrUrl);else image.src=imageOrFileOrUrl;return QrScanner._awaitImageLoad(image).then(()=>{if(imageOrFileOrUrl instanceof File)URL.revokeObjectURL(image.src);return image})}else return Promise.reject("Unsupported image type.")}static _awaitImageLoad(image){return new Promise((resolve,
-reject)=>{if(image.complete&&image.naturalWidth!==0)resolve();else{let onLoad,onError;onLoad=()=>{image.removeEventListener("load",onLoad);image.removeEventListener("error",onError);resolve()};onError=()=>{image.removeEventListener("load",onLoad);image.removeEventListener("error",onError);reject("Image load error")};image.addEventListener("load",onLoad);image.addEventListener("error",onError)}})}}QrScanner.DEFAULT_CANVAS_SIZE=400;QrScanner.WORKER_PATH="/libraries/qr-scanner/qr-scanner-worker.min.js";
+'use strict';export default class QrScanner{static hasCamera(){return navigator.mediaDevices.enumerateDevices().then((devices)=>devices.some((device)=>device.kind==="videoinput")).catch(()=>false)}constructor(video,onDecode,canvasSize=QrScanner.DEFAULT_CANVAS_SIZE){this.$video=video;this.$canvas=document.createElement("canvas");this._onDecode=onDecode;this._active=false;this._paused=false;this.$canvas.width=canvasSize;this.$canvas.height=canvasSize;this._sourceRect={x:0,y:0,width:canvasSize,height:canvasSize};
+this._onCanPlay=this._onCanPlay.bind(this);this._onPlay=this._onPlay.bind(this);this._onVisibilityChange=this._onVisibilityChange.bind(this);this.$video.addEventListener("canplay",this._onCanPlay);this.$video.addEventListener("play",this._onPlay);document.addEventListener("visibilitychange",this._onVisibilityChange);this._qrWorker=new Worker(QrScanner.WORKER_PATH)}destroy(){this.$video.removeEventListener("canplay",this._onCanPlay);this.$video.removeEventListener("play",this._onPlay);document.removeEventListener("visibilitychange",
+this._onVisibilityChange);this.stop();this._qrWorker.postMessage({type:"close"})}start(){if(this._active&&!this._paused)return Promise.resolve();if(window.location.protocol!=="https:")console.warn("The camera stream is only accessible if the page is transferred via https.");this._active=true;this._paused=false;if(document.hidden)return Promise.resolve();clearTimeout(this._offTimeout);this._offTimeout=null;if(this.$video.srcObject){this.$video.play();return Promise.resolve()}let facingMode="environment";
+return this._getCameraStream("environment",true).catch(()=>{facingMode="user";return this._getCameraStream()}).then((stream)=>{this.$video.srcObject=stream;this._setVideoMirror(facingMode)}).catch((e)=>{this._active=false;throw e;})}stop(){this.pause();this._active=false}pause(){this._paused=true;if(!this._active)return;this.$video.pause();if(this._offTimeout)return;this._offTimeout=setTimeout(()=>{const track=this.$video.srcObject&&this.$video.srcObject.getTracks()[0];if(!track)return;track.stop();
+this.$video.srcObject=null;this._offTimeout=null},300)}static scanImage(imageOrFileOrUrl,sourceRect=null,worker=null,canvas=null,fixedCanvasSize=false,alsoTryWithoutSourceRect=false){const promise=new Promise((resolve,reject)=>{if(!worker){worker=new Worker(QrScanner.WORKER_PATH);worker.postMessage({type:"inversionMode",data:"both"})}let timeout,onMessage,onError;onMessage=(event)=>{if(event.data.type!=="qrResult")return;worker.removeEventListener("message",onMessage);worker.removeEventListener("error",
+onError);clearTimeout(timeout);if(event.data.data!==null)resolve(event.data.data);else reject("QR code not found.")};onError=(e)=>{worker.removeEventListener("message",onMessage);worker.removeEventListener("error",onError);clearTimeout(timeout);var errorMessage=!e?"Unknown Error":e.message||e;reject("Scanner error: "+errorMessage)};worker.addEventListener("message",onMessage);worker.addEventListener("error",onError);timeout=setTimeout(()=>onError("timeout"),3E3);QrScanner._loadImage(imageOrFileOrUrl).then((image)=>
+{const imageData=QrScanner._getImageData(image,sourceRect,canvas,fixedCanvasSize);worker.postMessage({type:"decode",data:imageData},[imageData.data.buffer])}).catch(reject)});if(sourceRect&&alsoTryWithoutSourceRect)return promise.catch(()=>QrScanner.scanImage(imageOrFileOrUrl,null,worker,canvas,fixedCanvasSize));else return promise}setGrayscaleWeights(red,green,blue){this._qrWorker.postMessage({type:"grayscaleWeights",data:{red,green,blue}})}setInversionMode(inversionMode){this._qrWorker.postMessage({type:"inversionMode",
+data:inversionMode})}_onCanPlay(){this._updateSourceRect();this.$video.play()}_onPlay(){this._updateSourceRect();this._scanFrame()}_onVisibilityChange(){if(document.hidden)this.pause();else if(this._active)this.start()}_updateSourceRect(){const smallestDimension=Math.min(this.$video.videoWidth,this.$video.videoHeight);const sourceRectSize=Math.round(2/3*smallestDimension);this._sourceRect.width=this._sourceRect.height=sourceRectSize;this._sourceRect.x=(this.$video.videoWidth-sourceRectSize)/2;this._sourceRect.y=
+(this.$video.videoHeight-sourceRectSize)/2}_scanFrame(){if(!this._active||this.$video.paused||this.$video.ended)return false;requestAnimationFrame(()=>{QrScanner.scanImage(this.$video,this._sourceRect,this._qrWorker,this.$canvas,true).then(this._onDecode,(error)=>{if(this._active&&error!=="QR code not found.")console.error(error)}).then(()=>this._scanFrame())})}_getCameraStream(facingMode,exact=false){const constraintsToTry=[{width:{min:1024}},{width:{min:768}},{}];if(facingMode){if(exact)facingMode=
+{exact:facingMode};constraintsToTry.forEach((constraint)=>constraint.facingMode=facingMode)}return this._getMatchingCameraStream(constraintsToTry)}_getMatchingCameraStream(constraintsToTry){if(constraintsToTry.length===0)return Promise.reject("Camera not found.");return navigator.mediaDevices.getUserMedia({video:constraintsToTry.shift()}).catch(()=>this._getMatchingCameraStream(constraintsToTry))}_setVideoMirror(facingMode){const scaleFactor=facingMode==="user"?-1:1;this.$video.style.transform="scaleX("+
+scaleFactor+")"}static _getImageData(image,sourceRect=null,canvas=null,fixedCanvasSize=false){canvas=canvas||document.createElement("canvas");const sourceRectX=sourceRect&&sourceRect.x?sourceRect.x:0;const sourceRectY=sourceRect&&sourceRect.y?sourceRect.y:0;const sourceRectWidth=sourceRect&&sourceRect.width?sourceRect.width:image.width||image.videoWidth;const sourceRectHeight=sourceRect&&sourceRect.height?sourceRect.height:image.height||image.videoHeight;if(!fixedCanvasSize&&(canvas.width!==sourceRectWidth||
+canvas.height!==sourceRectHeight)){canvas.width=sourceRectWidth;canvas.height=sourceRectHeight}const context=canvas.getContext("2d",{alpha:false});context.imageSmoothingEnabled=false;context.drawImage(image,sourceRectX,sourceRectY,sourceRectWidth,sourceRectHeight,0,0,canvas.width,canvas.height);return context.getImageData(0,0,canvas.width,canvas.height)}static _loadImage(imageOrFileOrUrl){if(imageOrFileOrUrl instanceof HTMLCanvasElement||imageOrFileOrUrl instanceof HTMLVideoElement||window.ImageBitmap&&
+imageOrFileOrUrl instanceof window.ImageBitmap||window.OffscreenCanvas&&imageOrFileOrUrl instanceof window.OffscreenCanvas)return Promise.resolve(imageOrFileOrUrl);else if(imageOrFileOrUrl instanceof Image)return QrScanner._awaitImageLoad(imageOrFileOrUrl).then(()=>imageOrFileOrUrl);else if(imageOrFileOrUrl instanceof File||imageOrFileOrUrl instanceof URL||typeof imageOrFileOrUrl==="string"){const image=new Image;if(imageOrFileOrUrl instanceof File)image.src=URL.createObjectURL(imageOrFileOrUrl);
+else image.src=imageOrFileOrUrl;return QrScanner._awaitImageLoad(image).then(()=>{if(imageOrFileOrUrl instanceof File)URL.revokeObjectURL(image.src);return image})}else return Promise.reject("Unsupported image type.")}static _awaitImageLoad(image){return new Promise((resolve,reject)=>{if(image.complete&&image.naturalWidth!==0)resolve();else{let onLoad,onError;onLoad=()=>{image.removeEventListener("load",onLoad);image.removeEventListener("error",onError);resolve()};onError=()=>{image.removeEventListener("load",
+onLoad);image.removeEventListener("error",onError);reject("Image load error")};image.addEventListener("load",onLoad);image.addEventListener("error",onError)}})}}QrScanner.DEFAULT_CANVAS_SIZE=400;QrScanner.WORKER_PATH="/libraries/qr-scanner/qr-scanner-worker.min.js";
 
 //# sourceMappingURL=qr-scanner.min.js.map

qr-scanner.min.js.map

@@ -1 +1 @@
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src/qr-scanner.js

@@ -1,4 +1,14 @@
 export default class QrScanner {
+    /* async */
+    static hasCamera() {
+        // note that enumerateDevices can always be called and does not prompt the user for permission. However, device
+        // labels are only readable if served via https and an active media stream exists or permanent permission is
+        // given. That doesn't matter for us though as we don't require labels.
+        return navigator.mediaDevices.enumerateDevices()
+            .then(devices => devices.some(device => device.kind === 'videoinput'))
+            .catch(() => false);
+    }
+
     constructor(video, onDecode, canvasSize = QrScanner.DEFAULT_CANVAS_SIZE) {
         this.$video = video;
         this.$canvas = document.createElement('canvas');

types/qr-scanner.d.ts

@@ -6,6 +6,8 @@ declare class QrScanner {
     static DEFAULT_CANVAS_SIZE: number;
     static WORKER_PATH: string;
 
+    static hasCamera(): Promise<boolean>;
+
     constructor(video: HTMLVideoElement, onDecode: Function, canvasSize?: number);
 
     destroy(): void;