function ellipse2path(cx, cy, rx, ry, degree) {
    //cx cy:圓心
    //rx ry:x y 軸長
    //degree:度數(shù)，順時針方向為正
    //思路：求出直線與橢圓的交點，然后從一端繪制到另一端
    //非數(shù)值單位計算，如當(dāng)寬度像100%則移除 
    if (isNaN(cx - cy + rx - ry))
        return;
    //逆時針繪制
    var radian = (Math.PI * 2 / 360) * degree
    var x1 = cx + rx * Math.cos(radian)
    var y1 = cx + rx * Math.sin(radian) //計算機Y軸正向向下
    var x2_relative = 2 * rx * Math.cos(radian)
    var y2_relative = -2 * rx * Math.sin(radian)

    var path = 'M' + x1 + ' ' + y1 +
        'a' + rx + ' ' + ry + ' ' + degree + ' 1 1 ' + x2_relative + ' ' + y2_relative + ' ' +
        'a' + rx + ' ' + ry + ' ' + degree + ' 1 1 ' + -1 * x2_relative + ' ' + -1 * y2_relative + ' ' + 'z';
    return path;
}