参考：
https://segmentfault.com/q/1010000006717959
问题：
a.获取的好像是第一帧的图？第一帧为透明图时，获取的个透明图片
b.得先加载视频到video,做视频上传的时候体验不太友好
c.qq空间能截取视频图片，不知道怎么实现的
<!DOCTYPE html><html><head> ???<meta charset="utf-8" /> ???<title></title></head><body><video id="video" controls="controls" width="400" height="300"> ???<source src="myvideo.mp4"></video><br><br>视频第一帧图片：<div id="output"></div><script type="text/javascript">(function(){var video, output;var scale = 0.8;var initialize = function() { ???output = document.getElementById("output"); ???video = document.getElementById("video"); ???video.addEventListener(‘loadeddata‘,captureImage);};var captureImage = function() { ???var canvas = document.createElement("canvas"); ???canvas.width = video.videoWidth * scale; ???canvas.height = video.videoHeight * scale; ???canvas.getContext(‘2d‘).drawImage(video, 0, 0, canvas.width, canvas.height); ????var img = document.createElement("img"); ???img.src = canvas.toDataURL("image/png"); ???img.width = 400; ???img.height = 300; ???output.appendChild(img);};initialize();})();</script></body></html>
js获取视频截图
原文地址：https://www.cnblogs.com/liuqiyun/p/9519842.html