已知两条cv::Vec4f表示的直线，求两条直线的交点

函数的返回值表示是否有交点

直线的交点由函数的最后一个参数通过引用返回

    static bool lineIntersection(const cv::Vec4f& lineA, const cv::Vec4f& lineB, cv::Point2f& p)
    {
        const float Eps = float(1e-8);
        ///first line
        float x1 = lineA[2];
        float y1 = lineA[3];
        float x2 = x1 + lineA[0];
        float y2 = y1 + lineA[1];

        ///second line
        float x3 = lineB[2];
        float y3 = lineB[3];
        float x4 = x3 + lineB[0];
        float y4 = y3 + lineB[1];

        ///then  find intersection

        ///denominator
        float den = ((x1 - x2) * (y3 - y4)) - ((y1 - y2) * (x3 - x4));
        if (fabs(den) <= Eps)
            return false;

        float d0 = (x1 * y2) - (y1 * x2);
        float d1 = (x3 * y4) - (y3 * x4);
        float numx = (d0 * (x3 - x4)) - (d1 * (x1 - x2));
        float numy = (d0 * (y3 - y4)) - (d1 * (y1 - y2));

        p.x = numx / den;
        p.y = numy / den;

        return true;
    }