取得CSS Rotation 百分比

//
// 取得旋轉角度
(function($){
    $.fn.rotationDegrees = function () {
        var matrix = this.css('-webkit-transform') ||
	    this.css('-moz-transform')    ||
	    this.css('-ms-transform')     ||
	    this.css('-o-transform')      ||
	    this.css('transform');
    if(typeof matrix === 'string' && matrix !== 'none') {
        var values = matrix.split('(')[1].split(')')[0].split(',');
        var a = values[0];
        var b = values[1];
        var angle = Math.round(Math.atan2(b, a) * (180/Math.PI));
    } else { var angle = 0; }
    return angle;
   };
}(jQuery));