Javascript：
Firefox3,IE6,IE7,IE8上传图片预览，这是一个比较实用的功能，暂时记录下来，以供参考：
<!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>
<title>Firefox3,IE6,IE7,IE8上传图片预览</title>
<style type="text/css">
#preview_wrapper{
display:inline-block;
width:300px;
height:300px;
background-color:#CCC;
}
#preview_fake{
/* 该对象用于在IE下显示预览图片
*/
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);
}
#preview_size_fake{
/* 该对象只用来在IE下获得图片的原始尺寸，无其它用途
*/
filter:progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=image);
visibility:hidden;
}
#preview{
/* 该对象用于在FF下显示预览图片
*/
width:300px;
height:300px;
}
</style>
<script type="text/javascript">
function onUploadImgChange(sender){
if( !sender.value.match(/.jpg|.gif|.png|.bmp/i)){
alert('图片格式无效！');
return false;
}
var objPreview = document.getElementById('preview' );
var objPreviewFake = document.getElementById('preview_fake' );
var objPreviewSizeFake = document.getElementById('preview_size_fake' );
if( sender.files &&sender.files[0] ){
objPreview.style.display ='block';
objPreview.style.width ='auto';
objPreview.style.height ='auto';
// Firefox 因安全性问题已无法直接通过input[file].value
objPreview.src =sender.files[0].getAsDataURL();
}else if( objPreviewFake.filters
){
// IE7,IE8 在设置本地图片地址为 img.src 时出现莫名其妙的后果
//（相同环境有时能显示，有时不显示），因此只能用滤镜来解决
// IE7, IE8因安全性问题已无法直接通过 input[file].value 获取完整的文件路径
sender.select();
var imgSrc =document.selection.createRange().text;
objPreviewFake.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src= imgSrc;
objPreviewSizeFake.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src= imgSrc;
autoSizePreview( objPreviewFake,objPreviewSizeFake.offsetWidth,objPreviewSizeFake.offsetHeight );
objPreview.style.display ='none';
}
}
function onPreviewLoad(sender)
{autoSizePreview(sender,sender.offsetWidth, sender.offsetHeight );}
function autoSizePreview( objPre, originalWidth, originalHeight){
var zoomParam = clacImgZoomParam( 300, 300, originalWidth,originalHeight);
objPre.style.width = zoomParam.width +'px';
objPre.style.height = zoomParam.height +'px';
objPre.style.marginTop = zoomParam.top +'px';
objPre.style.marginLeft = zoomParam.left + 'px';
}
function clacImgZoomParam( maxWidth, maxHeight, width, height ){
var param = { width:width, height:height, top:0, left:0 };
if(width>maxWidth || height>maxHeight ){
rateWidth = width /maxWidth;
rateHeight = height /maxHeight;
if( rateWidth > rateHeight){
param.width =maxWidth;
param.height = height /rateWidth;
}else{
param.width = width /rateHeight;
param.height =maxHeight;
}
}
param.left = (maxWidth - param.width) / 2;
param.top = (maxHeight - param.height) /2;
return param;
}
</script>
</head>
<body>
<div id="preview_wrapper">
<div id="preview_fake">
<img id="preview" onload="onPreviewLoad(this)"/>
</div>
</div>
<br/>
<input id="upload_img" type="file" onchange="onUploadImgChange(this)"/>
<br/>
<img id="preview_size_fake"/>
</body>
</html>