/**
 * @author Alexander Farkas
 * v. 1.02
 */
(function($) {
	$.extend($.fx.step,{
	    backgroundPosition: function(fx) {
            if (fx.state === 0 && typeof fx.end == 'string') {
                var start = $.curCSS(fx.elem,'backgroundPosition');
                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 = [];
			var tempA = ((fx.end[0] - fx.start[0]) * fx.pos) + fx.start[0];
			var tempB = ((fx.end[1] - fx.start[1]) * fx.pos) + fx.start[1];
			
			if(!isNaN(tempA) && !isNaN(tempB)){
				nowPosX[0] =  tempA + fx.unit[0];
				nowPosX[1] =  tempB + 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)/);
			   if(res == null){
					return 0;
			   }
               return [parseFloat(res[1],10),res[2],parseFloat(res[3],10),res[4]];
           }
        }
	});
})(jQuery);