HTML5 drawImage()方法将图像绘制到画布上
要将图像绘制到画布上，请使用HTML5drawImage()方法：
<!DOCTYPE HTML>
<html>
<head>
<script>
function drawShape(){
//使用DOM获取canvas元素
var canvas = document.getElementById('mycanvas');
//确保不支持画布时不执行
if (canvas.getContext){
//使用getContext将画布用于绘制
var ctx = canvas.getContext('2d');
//绘制形状
var img = new Image();
img.src = '/images/backdrop.jpg';
img.onload = function(){
ctx.drawImage(img,0,0);
ctx.beginPath();
ctx.moveTo(30,96);
ctx.lineTo(70,66);
ctx.lineTo(103,76);
ctx.lineTo(170,15);
ctx.stroke();
}
} else {
alert('You need Safari or Firefox 1.5+ to see this demo.');
}
}
</script>
</head>
<body onload = "drawShape();">
<canvas id = "mycanvas"></canvas>
</body>
</html>