略微修改了一下：
<img src="1.jpg">
<SCRIPT LANGUAGE="JavaScript">
document.ondblclick = function()
{
  var e = window.event.srcElement;
  if(e.tagName=="IMG")
  {
    var win=window.open(e.src, "_blank", "top=1200px,left=1200px");
    win.document.execCommand('SaveAs');
    win.opener=null;
    win.close();
  }
}
</SCRIPT>