drawImage方法
context.drawImage(image,sx,sy,sh,dx,dy,dw,dh)
sxsy起始图像的横纵坐标，shsd起始图像的大小，dxdy复制图像的横纵坐标，dwdy复制图像的大小
下面我们用这个属性来做一个点击局部放大效果
<!DOCTYPE html>
<html>
<head>
<title></title>
<script type="text/javascript" src="js/jquery.js"></script>
<script type="text/javascript">
var context;
var canvas;
var iMouseX, iMouseY = 1;
var image;
//绘制区域
window.onload = function() {
function draw(id){
canvas = document.getElementById(id);
if(canvas == null)
return false;
context = canvas.getContext('2d');
context.fillStyle = "#eeeeff";
context.fillRect(0,0,400,300);
//一边装载，一边绘制
image = new Image();
image.src = "img/2.png";
image.onload = function() {
drawImg(context,image);
};
}
//将原始图片添加到网页上
function drawImg(context,image) {
context.drawImage(image,0,0,100,100);
}
draw('canvas');
//点击原始图片放大事件
canvas.onclick = function(e) {//监听鼠标动作
iMouseX = Math.floor(e.pageX);
iMouseY = Math.floor(e.pageY)-82;
context.drawImage(image,iMouseX,iMouseY,57,80,110,0,200,200);
}
}
</script>
</head>
<body>
<h1>canvas元素示例</h1>
<canvas id="canvas" width="400" height="300" ></canvas>
</body>
</html>