function image_open(image_url,w,h)
{
	sw = screen.width;
	sh = screen.height;
	if(w>=sw)
	{
		wx = 0;
		sb = 1;
		w += 15;
	}
	else
	{
		wx = Math.round((sw-w)/2);
		sb = 0;
	}
	if(h>=sh)
	{
		wy = 0;
		sb = 1;
		h += 15;
	}
	else
	{
		wy = Math.round((sh-h)/2);
	}
	attributes_string = 'width='+w+',height='+h+',left='+wx+',top='+wy+',buttons=0,directories=0,location=0,menubar=0,resizable=0,scrollbars=0'+sb;
	image_win = window.open(image_url, 'image_win', attributes_string);
}