/**  
 * @author Alexander Farkas  
 * v. 1.03  
 */ 
(function($) {  
	$.extend($.fx.step,{  
		backgroundPosition: function(fx) {
			if (fx.state === 0 && typeof fx.end == 'string') {
				var start = $.curCSS(fx.elem,'backgroundPosition');
				if(!start){
					start = '0px 0px';
					};
				start = toArray(start);
				fx.start = [start[0],start[2]];
				var end = toArray(fx.end);
				fx.end = [end[0],end[2]];
				fx.unit = [end[1],end[3]];
			}
			var nowPosX = [];
			nowPosX[0] = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0] + fx.unit[0];
			nowPosX[1] = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1] + fx.unit[1];
			fx.elem.style.backgroundPosition = nowPosX[0]+' '+nowPosX[1];
			
			function toArray(strg){
				strg = strg.replace(/left|top/g,'0px');
				strg = strg.replace(/right|bottom/g,'100%');
				strg = strg.replace(/([0-9\.]+)(\s|\)|$)/g,"$1px$2");
				var res = strg.match(/(-?[0-9\.]+)(px|\%|em|pt)\s(-?[0-9\.]+)(px|\%|em|pt)/);
				return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
				} 
			}
		});  
})(jQuery);