Puoi sempre usare il javascript

codice:
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">

<html>
<head>
<title>Untitled</title>
<script language="JavaScript" type="text/javascript">
<!--
function resizeImage(aWidth,aHeight) {
 oColl     = document.getElementsByTagName('IMG');
 len       = oColl.length;
 for (i=0;i<len;i++) {
  curObj = oColl.item(i);
	if (curObj.width > aWidth || curObj.height > aHeight) {
   curObj.width  = aWidth;
	 curObj.height = aHeight;
	} // if (curObj.width > aWidth || curObj.height > aHeight)
 } // for (i=0;i<len;i++) 
} // function resizeImage(aWidth,aHeight)
//-->
</script>

</head>
<body onload="resizeImage(100,100)">



</body>
</html>