/**
 * @author Alexander Farkas
 * v. 1.02
 */
(function(jQuery) {
	jQuery.extend(jQuery.fx.step,{
		backgroundPosition: function(fx) {
			if (fx.state === 0 && typeof fx.end == 'string') {
				var start = jQuery.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){
				try {
					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]];
				} catch(Error) {return new Array(0,0,0,0);}
			}
		}
	});
})(jQuery);