<form action="p1.html" id="form" ENCTYPE="multipart/form-data" method="post">
<input type="file" name="f" style="display:none" id="g" onchange="F_sub()">
<img src="2.jpg" onclick="F_Open_dialog()" >
</form>

<script type="text/javascript">
    function F_Open_dialog() 
    { 
      document.getElementById("g").click();
      
      
    } 
    function F_sub(){
      var v=document.getElementById("g").value;
       if(v=="")return;
       else document.getElementById("form").submit(); 
    }
 </script>