可预览缩略图（实时预览）的上传图片界面

<script language=JavaScript>
var flag=false;
function DrawImage(ImgD){
   var image=new Image();
   image.src=ImgD.src;
   if(image.width>0 && image.height>0){
    flag=true;
    if(image.width/image.height>= 120/80){
     if(image.width>120){ 
     ImgD.width=120;
     ImgD.height=(image.height*120)/image.width;
     }else{
     ImgD.width=image.width; 
     ImgD.height=image.height;
     }
     ImgD.alt=image.width+"×"+image.height;
     }
    else{
     if(image.height>80){ 
     ImgD.height=80;
     ImgD.width=(image.width*80)/image.height;    
     }else{
     ImgD.width=image.width; 
     ImgD.height=image.height;
     }
     ImgD.alt=image.width+"×"+image.height;
     }
    }
   /*else{
    ImgD.src="";
    ImgD.alt=""
    }*/
   }

function FileChange(Value){
flag=false;
document.all.uploadimage.width=10;
document.all.uploadimage.height=10;
document.all.uploadimage.alt="";
document.all.uploadimage.src=Value;
}

function BeforeUpLoad(){
if(flag) alert("OK");else alert("FAIL");
}
</script>
<INPUT style="WIDTH: 143px; HEIGHT: 18px" type=file size=8 name=pic onchange="javascript:FileChange(this.value);">
<IMG id=uploadimage height=10 width=10 src=""  onload="javascript:DrawImage(this);" ><BR>
<Button onclick="javascript:BeforeUpLoad();">提交</Button>