关于上传图片预览的问题

为什么这段代码老报错呢，不知道错在哪里...<script>
function SeePicNew(imgdid,f) {
    if(f.value=='') return ;
    var newPreview = document.getElementById(imgdid);
    var filepath = 'file:///'+f.value.replace(/\\/g,"/").replace(/\:/,"|");
    var image = new Image(); var ImgD = new Image();
    ImgD.src = filepath;
    image.src = ImgD.src; FitWidth = 150; FitHeight = 100;
    if(image.width>0 && image.height>0)
    {
         if(image.width/image.height>= FitWidth/FitHeight)
         {
             if(image.width>FitWidth)
             {
                 ImgD.width=FitWidth;
                 ImgD.height=(image.height*FitWidth)/image.width;
             }
             else
             {
                 ImgD.width=image.width; 
                ImgD.height=image.height;
             }
         }
         else
         {
            if(image.height>FitHeight)
            {
                 ImgD.height=FitHeight;
                 ImgD.width=(image.width*FitHeight)/image.height;
            }
            else
            {
                 ImgD.width=image.width; 
                ImgD.height=image.height;
            } 
        }
    }
    
    newPreview.style.width = ImgD.width+"px";
    newPreview.style.height = ImgD.height+"px";
    if(window.navigator.userAgent.indexOf("MSIE") < 1)
    {
        newPreview.style.background = "url('"+ImgD.src+"') no-repeat";    
    }
    else
    {
        newPreview.style.filter = "progid:DXImageTransform.Microsoft.AlphaImageLoader(src='"+ImgD.src+"',sizingMethod='scale')";
    }
    
    ImgD = image = null;
    //newPreview.filters.item('DXImageTransform.Microsoft.AlphaImageLoader').src = f.value;
}
    
</script>
<input name="" type="file" onchange="SeePicNew(divpicview1,this)" />
<div id='divpicview1'></div>