code: function oval2contour(cx, cy, rx, ry) {
  
      if (undefined === ry) {
          ry = rx;
      }
  
      var bound = computeBoundingBox.computePath(circlePath);
      var scaleX = (+rx) * 2 / bound.width;
      var scaleY = (+ry) * 2 / bound.height;
      var centerX = bound.width * scaleX / 2;
      var centerY = bound.height * scaleY / 2;
      var contour = lang.clone(circlePath);
      pathAdjust(contour, scaleX, scaleY);
      pathAdjust(contour, 1, 1, +cx - centerX, +cy - centerY);
  
      return contour;
  }
docs: 椭圆转换成轮廓
  
  @param {number} cx 椭圆中心点x
  @param {number} cy 椭圆中心点y
  @param {number} rx 椭圆x轴半径
  @param {number} ry 椭圆y周半径
  @return {Array} 轮廓数组