/*
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>
