<html>
<body style="margin: 0;">
<svg xmlns="http://www.w3.org/2000/svg">
<!-- The FO's red half should be filtered to white, with only the green half visible. -->
<defs>
<filter id="filter" width="200" height="10">
    <feColorMatrix type="matrix" values="1,0,0,0,0, 1,1,0,0,0, 1,0,1,0,0, 0,0,0,1,0"/>
</filter>
</defs>
<foreignObject width="200" height="100" filter="url(#filter)" opacity=".5">
    <html xmlns="http://www.w3.org/1999/xhtml">
    <body>
        <div style="background: green; height: 50px;"></div>
        <div style="background: red; height: 50px;"></div>
    </body>
    </html>
</foreignObject>
</svg>
</body>
</html>