/**
* @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 = [];
        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);