zoom=100;
var tiempo;
function reduce(obj) {
  if(zoom>50) zoom-=10;
	obj.style.width=zoom;
	obj.style.height=zoom;
	im=obj;
	tiempo=setTimeout('reduce(im)',250);
}
function amplia(obj) {
	obj.style.width=100;
	obj.style.height=100;
	zoom=100;
	clearTimeout(tiempo)
}