OpenCV average direction/angle of line(s)

Question

Im trying to get the angle of the line(s) on each side of my path so I can determine where to go (I want to make sure Im driving straight down it).

In the first image, the "average" direction should be straight down the middle (90deg). In the second, it should be pointing a bit right (60deg).

The way I did it up to now was split the image into two halves, and count the white pixels on each side. If there were more on the left, it would turn right, if there were more on the right, it would turn left.

This has many downsides, though. Can anyone suggest a better way?

Answer 1

By eroding and boxing the resulting points, you can calculate the angle:

    cv::Mat img = cv::imread(filename, 0);
    .
    .
    .
    cv::Mat element = cv::getStructuringElement(cv::MORPH_RECT, cv::Size(5, 3));
    cv::erode(img, img, element);

    std::vector<cv::Point> points;
    cv::Mat_<uchar>::iterator it = img.begin<uchar>();
    cv::Mat_<uchar>::iterator end = img.end<uchar>();

    for (; it != end; ++it)
       if (*it)
          points.push_back(it.pos());

    cv::RotatedRect box = cv::minAreaRect(cv::Mat(points));

    double angle = box.angle;
    if (angle < -45.)
       angle += 90.;

OpenCV Bouding Box & Skew Angle