(function($){
	$.fn.imgBg=function(){
		var bgImg=$(this);
		bgImg.addClass('cm_imgBg');
		function resizeImg(){
			var imgwidth=bgImg.width();
			var imgheight=bgImg.height();
			var winwidth=$(window).width();
			var winheight=$(window).height();
			var widthratio=winwidth/imgwidth;
			var heightratio=winheight/imgheight;
			var widthdiff=heightratio*imgwidth;
			var heightdiff=widthratio*imgheight;
			if (heightdiff>winheight){
				bgImg.css({width:winwidth+'px',height:heightdiff+'px'});
				} else {
					bgImg.css({width:widthdiff+'px',height:winheight+'px'});
					}
			}	
		resizeImg();
		$(window).resize(function(){
			resizeImg();
		});
	};
})(jQuery)