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function getPolygonAreaCenter(points) {
    var sum_x = 0;
    var sum_y = 0;
    var sum_area = 0;
    var p1 = points[1];
    for (var i = 2; i < points.length; i++) {
        p2 = points[i];
        area = Area(points[0], p1, p2);
        sum_area += area;
        sum_x += (points[0].x + p1.x + p2.x) * area;
        sum_y += (points[0].y + p1.y + p2.y) * area;
        p1 = p2;
    }
    var xx = sum_x / sum_area / 3;
    var yy = sum_y / sum_area / 3;
    return { xx, yy };
}
function Area(p0, p1, p2) {
    var area = 0.0;
    area =
        p0.x * p1.y +
        p1.x * p2.y +
        p2.x * p0.y -
        p1.x * p0.y -
        p2.x * p1.y -
        p0.x * p2.y;
    return area / 2;
}