/*
网上百度的，感觉”从中间到两边“的效果写的不是很好，改了一下，感觉可以了！
*/
<html>
<head>
<title></title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
<script type="text/javascript">
var image;
var intervalId1;
var intervalId2;
var intervalId3;
var drawW1 = 0;
var canvas;
var context;
var drawLeft;
var baiyechuangItemW ;
function init(){
image = new Image();
image.src="eg_mouse.jpg";
canvas = document.getElementById("canvas1");
context = canvas.getContext("2d");
drawLeft = image.width/2;
}
function startLeftToRight(){
clearInterval(intervalId1);
context.clearRect(0,0,image.width,image.height);
intervalId1 = setInterval("leftToRight();",50);
}
function leftToRight(){
context.drawImage(image,0,0,drawW1, image.height,0,0,drawW1,image.height);
drawW1 += 2;
if(drawW1>image.width){
drawW1 =0;
clearInterval(intervalId1);
}
}
function centerToOuter(){
drawW1 += 2;
//drawLeft-drawW1/2是左端点，drawLeft是中间， drawLeft+drawW1/2是右端点
context.drawImage(image,drawLeft-drawW1/2,0,drawW1,image.height,drawLeft-drawW1/2,0,drawW1,image.height);
if(drawW1>drawLeft*2){
drawW1 = 0;
clearInterval(intervalId2);
}
}
function startCenterToOuter(){
clearInterval(intervalId2);
context.clearRect(0,0,image.width,image.height);
intervalId2 = setInterval("centerToOuter();",50);
}
function baiyechuang(){
for(i=0;i<10;i++){
context.drawImage(image,baiyechuangItemW*i,0,drawW1,image.height,baiyechuangItemW*i,0,drawW1,image.height);
}
drawW1 += 0.2;
if(drawW1>baiyechuangItemW){
clearInterval(intervalId3);
}
}
function startBaiyechuang(){
drawW1=0;
baiyechuangItemW = image.width/10.0;
clearInterval(intervalId3);
context.clearRect(0,0,image.width,image.height);
intervalId3 = setInterval("baiyechuang();", 50);
}
</script>
</head>
<body onload="init();">
<h1><input type="button" value="从左到右装载图片" onclick="startLeftToRight();"/></h1>
<h1><input type="button" value=“从中间到两边加载图片" onclick="startCenterToOuter();"/></h1>
<h1><input type="button" value="百叶窗方式装载图片" onclick="startBaiyechuang();"/></h1>
<div>
<canvas id="canvas1" width="400px" height="400px"></canvas>
</div>
</body>
</html>