#include <vector>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <math.h>

using namespace std;

void dostuff();

int main()
{
    dostuff();
    return 0;
}

typedef std::vector<cv::Point> vectorOfCvPoints;

void dostuff()
{

    const double ellipseCenterX = 250;
    const double ellipseCenterY = 250;
    const double ellipseRadiusX = 150;
    const double ellipseRadiusY = 100;

    vectorOfCvPoints datapoints;

    for (int i = 0; i < 360; i+=5)
    {
        double angle = i / 180.0 * CV_PI;
        double x = ellipseRadiusX * cos(angle);
        double y = ellipseRadiusY * sin(angle);
        x *= 1.4;
        y *= 1.4;
        x += ellipseCenterX;
        y += ellipseCenterY;
        datapoints.push_back(cv::Point(x,y));
    }

    cv::Mat drawing = cv::Mat::zeros( 500, 500, CV_8UC1 );

    for (int i = 0; i < datapoints.size(); i++)
    {
        const cv::Point & curPoint = datapoints[i];
        const double curPointX = curPoint.x;
        const double curPointY = curPoint.y * -1; //transform from image coordinates to geometric coordinates

        double angleToEllipseCenter = atan2(curPointY - ellipseCenterY * -1, curPointX - ellipseCenterX); //ellipseCenterY * -1 for transformation to geometric coords (from image coords)

        double nearestEllipseX = ellipseCenterX + ellipseRadiusX * cos(angleToEllipseCenter);
        double nearestEllipseY = ellipseCenterY * -1 + ellipseRadiusY * sin(angleToEllipseCenter); //ellipseCenterY * -1 for transformation to geometric coords (from image coords)


        cv::Point center(ellipseCenterX, ellipseCenterY);
        cv::Size axes(ellipseRadiusX, ellipseRadiusY);
        cv::ellipse(drawing, center, axes, 0, 0, 360, cv::Scalar(255));
        cv::line(drawing, curPoint, cv::Point(nearestEllipseX,nearestEllipseY*-1), cv::Scalar(180));

    }
    cv::namedWindow( "ellipse", CV_WINDOW_AUTOSIZE );
    cv::imshow( "ellipse", drawing );
    cv::waitKey(0);
}