兼容IE和FF的圖片上傳前預覽js代碼

更新時間：2013年05月28日 17:06:51 作者：

上傳前預覽使用js實現還是比較cool的，同時還可以兼容IE和FF的能做到這一點已經相當不容易了，下面與大家一起分享下具體的實現，感興趣的你可不要錯過了哈

效果圖如下：

代碼如下：

復制代碼代碼如下:

 
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"> 
<html xmlns="http://www.w3.org/1999/xhtml" > 
<head> 
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" /> 
<title>本地圖片預覽</title> 
<style type="text/css"> 
#preview{width:100px;height:100px;border:1px solid #000;overflow:hidden;} 
#imghead {filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);} 
</style> 
<script type="text/javascript"> 
function previewImage(file) 
{ 
var MAXWIDTH = 100; 
var MAXHEIGHT = 100; 
var div = document.getElementById('preview'); 
if (file.files && file.files[0]) 
{ 
div.innerHTML = '<img id=imghead>'; 
var img = document.getElementById('imghead'); 
img.onload = function(){ 
var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); 
img.width = rect.width; 
img.height = rect.height; 
img.style.marginLeft = rect.left+'px'; 
img.style.marginTop = rect.top+'px'; 
} 
var reader = new FileReader(); 
reader.onload = function(evt){img.src = evt.target.result;} 
reader.readAsDataURL(file.files[0]); 
} 
else 
{ 
var sFilter='filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale,src="'; 
file.select(); 
var src = document.selection.createRange().text; 
div.innerHTML = '<img id=imghead>'; 
var img = document.getElementById('imghead'); 
img.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = src; 
var rect = clacImgZoomParam(MAXWIDTH, MAXHEIGHT, img.offsetWidth, img.offsetHeight); 
status =('rect:'+rect.top+','+rect.left+','+rect.width+','+rect.height); 
div.innerHTML = "<div id=divhead style='width:"+rect.width+"px;height:"+rect.height+"px;margin-top:"+rect.top+"px;margin-left:"+rect.left+"px;"+sFilter+src+"\"'></div>"; 
} 
} 
function clacImgZoomParam( maxWidth, maxHeight, width, height ){ 
var param = {top:0, left:0, width:width, height:height}; 
if( width>maxWidth || height>maxHeight ) 
{ 
rateWidth = width / maxWidth; 
rateHeight = height / maxHeight; 

if( rateWidth > rateHeight ) 
{ 
param.width = maxWidth; 
param.height = Math.round(height / rateWidth); 
}else 
{ 
param.width = Math.round(width / rateHeight); 
param.height = maxHeight; 
} 
} 

param.left = Math.round((maxWidth - param.width) / 2); 
param.top = Math.round((maxHeight - param.height) / 2); 
return param; 
} 
</script> 
</head> 
<body> 
<div id="preview"> 
<img id="imghead" width=100 height=100 border=0 src='../images/head01_big.jpg'> 
</div> 
<br/> 
<input type="file" onchange="previewImage(this)" /> 
</body> 
</html> 