static std::array<int, 3> cross(const std::array<int, 3> &a,
	const std::array<int, 3> &b)
{
	std::array<int, 3> result;
	result[0] = a[1] * b[2] - a[2] * b[1];
	result[1] = a[2] * b[0] - a[0] * b[2];
	result[2] = a[0] * b[1] - a[1] * b[0];
	return result;
}

static double point_to_line_distance(const cv::Point &p, const cv::Vec4i &line)
{
	std::array<int, 3> pa{ { line[0], line[1], 1 } };
	std::array<int, 3> pb{ { line[2], line[3], 1 } };
	std::array<int, 3> l = cross(pa, pb);
	return std::abs((p.x * l[0] + p.y * l[1] + l[2])) * 1.0 /
		std::sqrt(double(l[0] * l[0] + l[1] * l[1]));
}