Something

<html>
<head>
<title></title>
<script type="text/javascript" language="Javascript">
var htmldocument=document;
var svgdoc='',root='';

function zoom(k)
	{
		svgdoc=htmldocument.getElementById("svgtest").getSVGDocument();
		root=svgdoc.firstChild();
		var old_value=root.currentScale;
		new_value=old_value * k;
		root.currentScale=new_value;
	}

function reset()
	{
		svgdoc=htmldocument.getElementById("svgtest").getSVGDocument();
		root=svgdoc.firstChild();
		//root.currentTranslate.x=0;
		//root.currentTranslate.y=0;
		root.currentScale=1;
	}
</script>
</head>
<body>
<h1>This is a SVG / Javascript test</h1>
<button onclick="zoom(2)">+</button> <button onclick="zoom(0.5)">-</button> <button onclick="reset()">reset</button>
<embed id="svgtest" width="450" height="370" src="test.svg" style="float: left" align="left">
</body>
</html>