navigator.mediaDevices.getUserMedia
應(yīng)項(xiàng)目要求，需要實(shí)現(xiàn)移動(dòng)端app嵌入H5頁(yè)面完成實(shí)人認(rèn)證的功能。打開(kāi)getUserMedia文檔，鏈接如下：
https://developer.mozilla.org/zh-CN/docs/Web/API/MediaDevices/getUserMedia
看上去很簡(jiǎn)單，最終卻寫(xiě)的懷疑人生。
API環(huán)境
問(wèn)題一：（為什么不管怎么配置都顯示前置攝像頭）
想正常使用API必須在https環(huán)境下進(jìn)行，否則你會(huì)發(fā)現(xiàn)不管怎么寫(xiě)，都只能調(diào)用默認(rèn)的攝像頭（大部分都是前置，只有少部分是后置）
前端開(kāi)發(fā)者可以將文件上傳至"碼云"倉(cāng)庫(kù)，獲取https鏈接然后在手機(jī)上預(yù)覽
鏈接：碼云倉(cāng)庫(kù)入口
問(wèn)題二：（API在安卓和ios效果一樣嗎？）
根據(jù)官方文檔，目前navigator.mediaDevices.getUserMedia在ios上只支持11版本以上，且只能在safari正常運(yùn)行。安卓目前沒(méi)有發(fā)現(xiàn)版本限制，需要兼容的代碼如下
if (navigator.mediaDevices === undefined) {
navigator.mediaDevices = {};
}
if (navigator.mediaDevices.getUserMedia === undefined) {
navigator.mediaDevices.getUserMedia = function (constraints) {
var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia || navigator.oGetUserMedia;
if (!getUserMedia) {
return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
}
return new Promise(function (resolve, reject) {
getUserMedia.call(navigator, constraints, resolve, reject);
});
}
}
問(wèn)題三：（第一次啟用成功調(diào)用前置攝像頭，第二次需要調(diào)用后置卻黑屏或者失敗）
失敗的原因很多，列舉兩個(gè)一開(kāi)始我遇到的問(wèn)題
1.前置攝像頭調(diào)用后，攝像功能需要關(guān)閉后才能正常執(zhí)行第二次調(diào)用，否則會(huì)報(bào)錯(cuò)：設(shè)備被占用。解決方法，在每次執(zhí)行調(diào)用方法前，先關(guān)閉攝像設(shè)備。
if (window.stream) {
window.stream.getTracks().forEach(track => {
track.stop();
});
}
親測(cè)有用，別的找了很多停止的方法都沒(méi)有效果。
2.調(diào)用后置API的方法還是無(wú)法喚醒后置攝像頭，于是我找到另外一個(gè)方法，通過(guò)查看手機(jī)攝像頭ID，來(lái)直接喚醒后置。
var deviceInfoId="", //攝像頭ID
num = 0, //攝像頭數(shù)量
carema = []; //攝像頭ID數(shù)組
//在頁(yè)面加載完成后獲得設(shè)備ID數(shù)組
window.onload = navigator.mediaDevices.enumerateDevices().then(gotDevices);
function gotDevices(deviceInfos) {
for (let i = 0; i < deviceInfos.length; ++i) {
if (deviceInfos[i].kind === 'videoinput') {
carema.push(deviceInfos[i].deviceId)
}
}
deviceInfoId = carema[后置位置];
}
var constraints = {
audio: false,
video: {
deviceId: deviceInfoId,
//放在app里面需要下面配置一下
"permissions": {
"audio-capture": {
"description": "Required to capture audio using getUserMedia()"
},
"video-capture": {
"description": "Required to capture video using getUserMedia()"
}
}
}
};
navigator.mediaDevices.getUserMedia(constraints)
.then(function (stream) {
var video = document.getElementById('video');
try {
window.stream = stream;
video.srcObject = stream;
} catch (error) {
video.src = window.URL.createObjectURL(stream);
}
this.localMediaStream = stream;
// video.play(); 這個(gè)加不加好像沒(méi)有影響
})
.catch(function (err) {
console.log(err.name + ": " + err.message);
});
如果只是一部手機(jī)可以這樣，但是測(cè)試了多部手機(jī)發(fā)現(xiàn)攝像頭數(shù)組毫無(wú)規(guī)律可循，這個(gè)方法慎用。
如果頁(yè)面上添加選擇攝像設(shè)備的按鈕的話，這個(gè)方法還是不錯(cuò)的。查看設(shè)備能調(diào)用幾個(gè)攝像頭鏈接如下：https://webrtc.github.io/samples/src/content/devices/input-output/
由于我們的項(xiàng)目頁(yè)面不希望出現(xiàn)切換按鈕，面對(duì)后置出現(xiàn)的眾多BUG，最終選擇放棄，使用input調(diào)用攝像頭。
<input class="card_input" v-on:change="appCapture($event)" type="file" accept="image/*" capture="camera" />
成功調(diào)用后用canvas實(shí)現(xiàn)成像并適應(yīng)屏幕大小
我這里的代碼是取video的寬高然后復(fù)制給canvas，這樣可以讓canvas和video保持一致，只用給video設(shè)置寬度100%，高度調(diào)節(jié)成合適的值，就實(shí)現(xiàn)了適應(yīng)手機(jī)屏幕。
var video = document.getElementById('video');
var canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d'),
CHeight = video.clientHeight, //獲取屏幕大小讓canvas自適應(yīng)
CWidth = video.clientWidth;
canvas.width = CWidth;
canvas.height = CHeight;
//localMediaStream 在data里定義一個(gè){}
if (localMediaStream) {
ctx.drawImage(video, 0, 0, CWidth, CHeight);
var dataURL = canvas.toDataURL('image/jpeg'); //dataURL = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA'
img.src = dataURL;
video成像鏡像問(wèn)題
API喚醒的前置攝像頭是相反的，很不舒服很不舒服。
之后用css處理一下給video添加 transform: rotate(180deg),可以實(shí)現(xiàn)反轉(zhuǎn)，但是還是沒(méi)有達(dá)到和手機(jī)一樣的效果。
這時(shí)候可以選擇通過(guò)設(shè)備ID調(diào)用前置攝像頭，前置攝像頭的laval一直都是“default”，也有的是空值，但是也能實(shí)現(xiàn)。
配置代碼如下：
var constraints = window.constraints = {
audio: false,
video: {
sourceId: 'default',
facingMode: { exact: "user" }
}
};
完美調(diào)用自己手機(jī)的前置攝像頭?。。?/p>
完整代碼如下：
頁(yè)面代碼：
<div @click='moveToCameraAVG()' v-cloak>
<img v-if="imginfo!==''" :src="imginfo" />
<div class="warm_title2">點(diǎn)擊自拍一張頭像</div>
</div>
<video id="video" class="pic_video" playsinline autoplay x5-video-player-type="h5" style='object-fit:fill'></video>
<canvas id="canvas" class="canvas_pic" style='margin: 0;padding: 0;'></canvas>
<div class="bottom_div">
<div>拍照</div>
<img src='images/pic_btn.png' class="capture-btn" @click='captureAvg' />
</div>
// 頭像相機(jī)
moveToCameraAVG() {
var self = this;
if (navigator.mediaDevices === undefined) {
navigator.mediaDevices = {};
}
if (navigator.mediaDevices.getUserMedia === undefined) {
navigator.mediaDevices.getUserMedia = function (constraints) {
var getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia || navigator.oGetUserMedia;
if (!getUserMedia) {
return Promise.reject(new Error('getUserMedia is not implemented in this browser'));
}
return new Promise(function (resolve, reject) {
getUserMedia.call(navigator, constraints, resolve, reject);
});
}
}
if (window.stream) {
window.stream.getTracks().forEach(track => {
track.stop();
});
}
var constraints = window.constraints = {
audio: false,
video: {
sourceId: 'default',
facingMode: { exact: "user" }
}
};
navigator.mediaDevices.getUserMedia(constraints)
.then(function (stream) {
var video = document.getElementById('video');
try {
window.stream = stream;
video.srcObject = stream;
} catch (error) {
video.src = window.URL.createObjectURL(stream);
}
self.localMediaStream = stream;
video.play();
})
.catch(function (err) {
alert(err.name + ": " + err.message);
});
},
//停止攝像機(jī)
stopCapture: function () {
var video = document.getElementById('video');
if (!video.srcObject) return
let stream = video.srcObject
let tracks = stream.getTracks();
tracks.forEach(track => {
track.stop()
})
},
// 頭像照片
captureAvg() {
var vm = this;
var video = document.getElementById('video');
var canvas = document.getElementById('canvas'),
ctx = canvas.getContext('2d'),
CHeight = video.clientHeight, //獲取屏幕大小讓canvas自適應(yīng)
CWidth = video.clientWidth;
canvas.width = CWidth;
canvas.height = CHeight;
if (vm.localMediaStream) {
ctx.drawImage(video, 0, 0, CWidth, CHeight);
var dataURL = canvas.toDataURL('image/jpeg'); //dataURL = 'data:image/png;base64,iVBORw0KGgoAAAANSUhEUgAA'
vm.imginfo = dataURL;
// 停止攝像機(jī)
video.pause();
this.stopCapture();
}
},
到此這篇關(guān)于HTML5通過(guò)navigator.mediaDevices.getUserMedia調(diào)用手機(jī)攝像頭問(wèn)題的文章就介紹到這了,更多相關(guān)HTML5調(diào)用 攝像頭內(nèi)容請(qǐng)搜索腳本之家以前的文章或繼續(xù)瀏覽下面的相關(guān)文章，希望大家以后多多支持腳本之家！
