function initImg(obj,w,h)
{
	var ow = obj.width ;
	var oh = obj.height ;
	if( ow > w || oh > h)
	{
		var ws = ow / w ;
		var hs = oh / h ;
		if( ws > hs)
		{
			obj.width = w ;
			obj.height = oh / ws;
		}
		else
		{
			obj.width = ow / hs ;
			obj.height = h ;
		}
	}
}