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DOLLOR #3 浏览器兼容性太差才是主要的，代码不复杂
直接手撸 getDisplayMedia 截屏：
```
navigator.mediaDevices.getDisplayMedia().then((stream)=>{
var canvas=document.createElement("canvas");
var video=document.createElement("video");
video.srcObject=stream;
var meta=stream.getVideoTracks()[0].getCapabilities();
video.width=canvas.width=meta.width.max;
video.height=canvas.height=meta.height.max;
video.onplay=()=>{ setTimeout(()=>{
canvas.getContext("2d").drawImage(video,0,0);
var b64=canvas.toDataURL("image/png");
document.body.innerHTML='<img src="'+b64+'">'
}, 1000)};
video.play();
}).catch((e)=>{ console.error(e) })
```