Question

I was looking for a helper function to calculate the intersection of two lines in OpenCV. I have searched the API Documentation, but couldn’t find a useful resource.

Are there basic geometric helper functions for intersection/distance calculations on lines/line segments in OpenCV?

Answer 1

There are no function in OpenCV API to calculate lines intersection, but distance is:

cv::Point2f start, end;
double length = cv::norm(end - start);

If you need a piece of code to calculate line intersections then here it is:

// Finds the intersection of two lines, or returns false.
// The lines are defined by (o1, p1) and (o2, p2).
bool intersection(Point2f o1, Point2f p1, Point2f o2, Point2f p2,
                      Point2f &r)
{
    Point2f x = o2 - o1;
    Point2f d1 = p1 - o1;
    Point2f d2 = p2 - o2;

    float cross = d1.x*d2.y - d1.y*d2.x;
    if (abs(cross) < /*EPS*/1e-8)
        return false;

    double t1 = (x.x * d2.y - x.y * d2.x)/cross;
    r = o1 + d1 * t1;
    return true;
}