class RectangleExt {
    /**
     * 计算两个矩形的并集。结果将是一个包含其他两个的矩形。
     * @param first 
     * @param point 
     */
    public static union(first: Rectangle, point: Vector2){
        let rect = new Rectangle(point.x, point.y, 0, 0);
        // let rectResult = first.union(rect);
        let result = new Rectangle();
        result.x = Math.min(first.x, rect.x);
        result.y = Math.min(first.y, rect.y);
        result.width = Math.max(first.right, rect.right) - result.x;
        result.height = Math.max(first.bottom, result.bottom) - result.y;
        return result;
    }
}