原文链接 http://lin.70apps.com/web/2014/11/27/html5-video-canvas-show.html
注：以下为加速网络访问所做的原文缓存，经过重新格式化，可能存在格式方面的问题，或偶有遗漏信息，请以原文为准。
HTML5中的canvas可以实现很多图像、多媒体方面的功能，比如把视频的内容二次处理后在canvas上显示。
强大的drawImage
var video = document.querySelector('video');
var canvas1 = document.querySelector('#canvas1');
var ctx1 = canvas1.getContext('2d');
ctx1.drawImage(video, 0,0, 320, 180, 0,0, 320, 180);
完整代码
<html >
<head>
<meta charset="utf-8" />
<title></title>
</head>
<body>
<div style="position:absolute;">
<input type="button" id="play" value="play">
<span id="position">00:00</span> / <span id="duration"></span>
</div>
<div style="position:absolute;top:350px;display:none;">
<video width="848" height="480" loop>
<source src="test.mp4" type="video/mp4"/>
</video>
</div>
<div style="position:absolute;left:10px;top:50px;">
<canvas id="canvas1" width="320" height="180"></canvas>
</div>
<div style="position:absolute;left:350px;top:50px;">
<canvas id="canvas2" width="320" height="180"></canvas>
</div>
<div style="position:absolute;left:10px;top:250px;">
<canvas id="canvas3" width="320" height="180"></canvas>
</div>
<div style="position:absolute;left:350px;top:250px;">
<canvas id="canvas4" width="320" height="180"></canvas>
</div>
<div style="position:absolute;left:10px;top:450px;">
<canvas id="canvas5" width="320" height="180"></canvas>
</div>
<div style="position:absolute;left:350px;top:450px;">
<canvas id="canvas6" width="320" height="180"></canvas>
</div>
<script >
var addEvent = (function () {
if (document.addEventListener) {
return function (el, type, fn) {
if (el && el.nodeName || el === window) {
el.addEventListener(type, fn, false);
} else if (el && el.length) {
for (var i = 0; i < el.length; i++) {
addEvent(el[i], type, fn);
}
}
};
} else {
return function (el, type, fn) {
if (el && el.nodeName || el === window) {
el.attachEvent('on' + type, function () { return fn.call(el, window.event); });
} else if (el && el.length) {
for (var i = 0; i < el.length; i++) {
addEvent(el[i], type, fn);
}
}
};
}
})();
</script>
<script>
var video = document.querySelector('video');
var togglePlay = document.querySelector('#play');
var position = document.querySelector('#position');
var canvas1 = document.querySelector('#canvas1');
var ctx1 = canvas1.getContext('2d');
var canvas2 = document.querySelector('#canvas2');
var ctx2 = canvas2.getContext('2d');
var canvas3 = document.querySelector('#canvas3');
var ctx3 = canvas3.getContext('2d');
var canvas4 = document.querySelector('#canvas4');
var ctx4 = canvas4.getContext('2d');
var canvas5 = document.querySelector('#canvas5');
var ctx5 = canvas5.getContext('2d');
var canvas6 = document.querySelector('#canvas6');
var ctx6 = canvas6.getContext('2d');
var vleft=10;
var vtop=80;
var vmargin=4;
var vwidth=392;
var vheight=156;
var canvaswidth=320;
var canvasheight=180;
addEvent(togglePlay, 'click', function () {
//video.playbackRate = 1;
if (video.paused) {
if (video.ended) video.currentTime = 0;
video.play();
this.value = "pause";
} else {
video.pause();
this.value = "play";
}
});
setInterval(function () {
position.innerHTML = asTime(video.currentTime);
ctx1.drawImage(video, vleft,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx2.drawImage(video, vleft+vwidth+vmargin,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx3.drawImage(video, vleft+vwidth*2+vmargin,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx4.drawImage(video, vleft, vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx5.drawImage(video, vleft+vwidth+vmargin,vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx6.drawImage(video, vleft+vwidth*2+vmargin,vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
}, 1000 / 25);
addEvent(video, 'ended', function () {
togglePlay.value = "play";
});
addEvent(video, 'canplay', function () {
video.muted = true;
document.querySelector('#duration').innerHTML = asTime(this.duration);
startCanvas();
});
function startCanvas() {
//canvas.setAttribute('height', Math.floor(video.height));
//canvas.setAttribute('width', Math.floor(video.width));
//ctx.translate(0, canvas.height );
//ctx.scale(1, -1);
//ctx.globalAlpha = 0.3;
ctx1.drawImage(video, vleft,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx2.drawImage(video, vleft+vwidth+vmargin,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx3.drawImage(video, vleft+vwidth*2+vmargin,vtop, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx4.drawImage(video, vleft, vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx5.drawImage(video, vleft+vwidth+vmargin,vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
ctx6.drawImage(video, vleft+vwidth*2+vmargin,vtop+vheight+vmargin, vwidth, vheight, 0,0, canvaswidth, canvasheight);
}
function asTime(t) {
t = Math.round(t);
var s = t % 60;
var m = Math.round(t / 60);
return two(m) + ':' + two(s);
}
function two(s) {
s += "";
if (s.length < 2) s = "0" + s;
return s;
}
</script>
</body>
</html>