var zoomlevel=1;
$("body").dblclick(function(ev) {
zoomlevel = zoomlevel == 1 ? 2 : 1;
$(this).css({
"-moz-transform":"scale("+zoomlevel+")",
"-webkit-transform":"scale("+zoomlevel+")",
"-o-transform":"scale("+zoomlevel+")",
"-ms-transform":"scale("+zoomlevel+")"
});
});