Mmmm... prova in questo modo:
codice:
<html>

<head>
	<meta http-equiv="content-type" content="text/html;charset=iso-8859-1">
	<title>ProvaPopUp</title>
	<script language="JavaScript">
	<!--
	function apriPopup(obj,w,h) {
		var theURL=obj.src;
		var pw=parseInt(w)+20;
		var ph=parseInt(h)+20;
		var poptions="directories=no,menubar=no,location=no,scrollbars=no,status=no,toolbar=no,resizable=no,width="+pw+",height="+ph;
		var myPopup=window.open('','myPopup',poptions);
		myPopup.document.write("[img]"+theURL+"[/img]");
	}
	//-->
	</script>
</head>

<body bgcolor="#ffffff">
	[img]img1.jpg[/img]
</body>

</html>