function show_image( url, w, h ){
	w = w + 20;
	h = h + 20;
	var sw = screen.width;
	var sh = screen.height;
	var k = w / h;
	var s = 0;
	if( w >= sw - 50 ){
		w = sw - 50;
		h = w / k;
		s = 1;
	}
	if( h >= sh -50 ){
		h = sh - 100;
		w = h * k;
		s = 1;
	}
	
	if( s ){
		w +=20;
		h += 20;
	}
	
	var l = ( sw - w )/2;
	var t = ( sh - h )/2 - 30;
	
	window.open(url,"_blank","toolbar=0,scrollbars="+s+",resizable=1,left="+l+",top="+t+", width="+w+",height="+h );
}