<table class="blue_table" cellpadding="0" cellspacing="0" border="0">
            <tr>
                <th colspan="2">添加商品图片</th>
            </tr>
            <tr>
                <td>
                    <div id="img_div" runat="server" style="filter: progid:DXImageTransform.Microsoft.AlphaImageLoader(sizingMethod=scale);width: 200px; height: 200px;margin:0 auto; margin-left:0px;border: 1px solid #e9ece5">
                        <img src="" runat="server"  alt="" />  
                    </div>
                </td>
            </tr>
            <tr>
                <td>
                    &nbsp;
                    <asp:FileUpload ID="FileUpload1" runat="server" onchange="showimg('FileUpload1','img_div',200,200)" size="7" class="input" />
                </td>
            </tr>
        </table>

**************************

function clearfile(file,img,width,height)
{
   document.getElementById(file).parentNode.style.display="";
   document.getElementById(file).parentNode.innerHTML='<input type="file" name="'+file+'" id="'+file+'" onchange="showimg(\''+file+'\',\''+img+'\')" size="7" class="input" />';
   document.getElementById(img).innerHTML="<img style='width:"+width+"px;height:"+height+"px' src='' />";
}
function showimg(file,img,width,height)
{ 
    var dFile = document.getElementById(file); 
    var dImg = document.getElementById(img);
    if(!getPath(dFile).match(/.jpg|.gif|.png|.bmp/i))
    {
        alert('上传图片格式必须是以下几种之一： .jpg , .gif , .bmp  或 .png !');
        clearfile(file,img);
        return;
    } 
    if(dFile.files)
    { 
        dImg.innerHTML="<img src='"+dFile.files[0].getAsDataURL()+"' style='width:"+width+"px;height:"+height+"px'/>";
    }
    else 
    {
        if(dFile.value.indexOf('\\') > -1 || dFile.value.indexOf('\/') > -1)
        {
            dImg.innerHTML="";
            dImg.filters.item("DXImageTransform.Microsoft.AlphaImageLoader").src = getPath(dFile);
        }
    }        
}
function getPath(obj)  
{    
    if(obj)      
    {       
        if (window.navigator.userAgent.indexOf("MSIE")>=1)        
        {          
            obj.select();         
            return document.selection.createRange().text;        
        }
        else if(window.navigator.userAgent.indexOf("Firefox")>=1)        
        {        
            if(obj.files)          
            {
                return obj.files.item(0).getAsDataURL();          
            }
            return obj.value;
        }   
        return obj.value;      
     } 
 }

本文转自94cool博客园博客，原文链接：http://www.cnblogs.com/94cool/archive/2010/10/12/1848874.html，如需转载请自行联系原作者