android截图canvas为空,安卓手机利用html5 ，video+canvas从视频流里面截图拍照

HTML5 GetUserMedia Demo

---

---

var video = document.querySelector('video');

var audio, audioType;

var canvas1 = document.getElementById('canvas1');

var context1 = canvas1.getContext('2d');

var canvas2 = document.getElementById('canvas2');

var context2 = canvas2.getContext('2d');

navigator.getUserMedia = navigator.getUserMedia || navigator.webkitGetUserMedia || navigator.mozGetUserMedia || navigator.msGetUserMedia;

window.URL = window.URL || window.webkitURL || window.mozURL || window.msURL;

var exArray = []; //存储设备源ID

MediaStreamTrack.getSources(function (sourceInfos) {

for (var i = 0; i != sourceInfos.length; ++i) {

var sourceInfo = sourceInfos[i];

//这里会遍历audio,video，所以要加以区分

if (sourceInfo.kind === 'video') {

exArray.push(sourceInfo.id);

}

}

});

function getMedia() {

if (navigator.getUserMedia) {

navigator.getUserMedia({

'video': {

'optional': [{

'sourceId': exArray[1] //0为前置摄像头，1为后置

}]

},

'audio':true

}, successFunc, errorFunc); //success是获取成功的回调函数

}

else {

alert('Native device media streaming (getUserMedia) not supported in this browser.');

}

}

function successFunc(stream) {

//alert('Succeed to get media!');

if (video.mozSrcObject !== undefined) {

//Firefox中，video.mozSrcObject最初为null，而不是未定义的，我们可以靠这个来检测Firefox的支持

video.mozSrcObject = stream;

}

else {

video.src = window.URL && window.URL.createObjectURL(stream) || stream;

}

//video.play();

// 音频

audio = new Audio();

audioType = getAudioType(audio);

if (audioType) {

audio.src = 'polaroid.' + audioType;

audio.play();

}

}

function errorFunc(e) {

alert('Error！'+e);

}

// 将视频帧绘制到Canvas对象上,Canvas每60ms切换帧，形成肉眼视频效果

function drawVideoAtCanvas(video,context) {

window.setInterval(function () {

context.drawImage(video, 0, 0,90,120);

}, 60);

}

//获取音频格式

function getAudioType(element) {

if (element.canPlayType) {

if (element.canPlayType('audio/mp4; codecs="mp4a.40.5"') !== '') {

return ('aac');

} else if (element.canPlayType('audio/ogg; codecs="vorbis"') !== '') {

return ("ogg");

}

}

return false;

}

// vedio播放时触发，绘制vedio帧图像到canvas

// video.addEventListener('play', function () {

// drawVideoAtCanvas(video, context2);

// }, false);

//拍照

function getPhoto() {

context1.drawImage(video, 0, 0,90,120); //将video对象内指定的区域捕捉绘制到画布上指定的区域，实现拍照。

}

//视频

function getVedio() {

drawVideoAtCanvas(video, context2);

}

经测试，支持pc+安卓手机，ios不支持这个方式。