H5 canvas参考手册

HTML 5 Canvas 参考手册

浏览器支持

Internet Explorer 9、Firefox、Opera、Chrome 以及 Safari 支持 <canvas> 及其属性和方法。

reference: 

            http://www.w3school.com.cn/tags/html_ref_canvas.asp

主要有4种绘法

chapter4:cxt.drawImage(img,0,0);

    

function getElementById(id){
    return document.getElementById(id);
}
var canvas = getElementById("canvas");
var cxt =  canvas.getContext("2d");

var img = new Image();
img.src = "../img/test3/cutegirl.png";
img.onload = function(e){
        cxt.drawImage(img,0,0);
}//用这种比较保险
cxt.drawImage(img,0,0);//sometime光用这种有不行

<p>要使用的视频：</p>
<video id="video1" controls width="270" autoplay>
  <source src="/example/html5/mov_bbb.mp4" type='video/mp4'>
  <source src="/example/html5/mov_bbb.ogg" type='video/ogg'>
  <source src="/example/html5/mov_bbb.webm" type='video/webm'>
</video>
<p>画布（每 20 毫秒，代码就会绘制视频的当前帧）：</p>
<canvas id="myCanvas" width="270" height="135" style="border:1px solid #d3d3d3;">
Your browser does not support the HTML5 canvas tag.

</canvas>

var v=document.getElementById("video1");
var c=document.getElementById("myCanvas");
ctx=c.getContext('2d');

var v=document.getElementById("video1");
var c=document.getElementById("myCanvas");
ctx=c.getContext('2d');

v.addEventListener('play', function () {
        var i = window.setInterval(function () {
                ctx.drawImage(v, 0, 0, 270, 135)
        }, 20);
}, false);
v.addEventListener('pause', function () {
        window.clearInterval(i);
}, false);
v.addEventListener('ended', function () {
        clearInterval(i);
}, false);