Firefox3,IE6,IE7,IE8上传图片预览

<!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>Firefox3,IE6,IE7,IE8上传图片预览</title>     
<style type="text/css">     
#preview_wrapper{      
    display:inline-block;      
    width:150px;      
    height:150px;      
    background-color:#CCC;      
}      
#preview_fake{ /* 该对象用户在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{ /* 该对象用户在FF下显示预览图片 */      
    width:150px;      
    height:150px;      
}      
</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 获取完整的文件路径      
        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( 150, 150, 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)" width="240px" height="240px" src="a.png"/>     
        </div>     
    </div>     
    <br/>     
    <input id="upload" type="file" onchange="onUploadImgChange(this)"/>     
    <br/>     
    <img id="preview_size_fake"/>     
</body>     
</html>