let video = document.querySelector('#movie_player > div.html5-video-container > video');
let canvas = document.createElement('canvas');
let a = document.createElement('a');
a.download = 'tmp.png';

canvas.width = 1920;
canvas.height = 1080;
let ctx = canvas.getContext('2d');
ctx.drawImage(video, 0, 0, canvas.width, canvas.height);

canvas.toBlob((blob) => {
	a.href = URL.createObjectURL(blob);
	a.click();
});