OpenCV C++ Code for drawing an Ellipse

Syntax:
C++ :void ellipse(Mat& img, Point center, Size axes, double angle, double startAngle, double endAngle, const Scalar& color, int thickness=1, int lineType=8, int shift=0)

Parameters:
img – Image.
center – Center of the ellipse.
axes – Half of the size of the ellipse main axes.
angle – Ellipse rotation angle in degrees.
startAngle – Starting angle of the elliptic arc in degrees.
endAngle – Ending angle of the elliptic arc in degrees.
box – Alternative ellipse representation via RotatedRect or CvBox2D. This means that the function draws an ellipse inscribed in the rotated rectangle.
color – Ellipse color.
thickness – Thickness of the ellipse arc outline, if positive. Otherwise, this indicates that a filled ellipse sector is to be drawn.
lineType – Type of the ellipse boundary. See the line() description.
shift – Number of fractional bits in the coordinates of the center and values of axes.

Note: If you want to draw the whole ellipse and not an arc, choose startAngle 0 and endAngle 360.

Note: CIRCLE is a special case of ELLIPSE whose ECCENTRICITY is equal to ONE.
i.e whose both the axis are of equal length.

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//Code for drawing an ellipse
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
using namespace cv;
int main( )
{
Mat image = Mat::zeros( 400, 400, CV_8UC3 );
//void ellipse(Mat& img, Point center, Size axes, double angle, double startAngle, double endAngle, const Scalar& color, int thickness=1*, int lineType=8*, int shift=0);
ellipse( image, Point( 200, 200 ), Size( 100.0, 150.0 ), 45, 0, 360, Scalar( 255, 0, 0 ), 3, 8 );
ellipse( image, Point( 200, 200 ), Size( 100.0, 150.0 ), 90, 0, 360, Scalar( 0,255, 0 ), 3, 8 );
ellipse( image, Point( 200, 200 ), Size( 100.0, 150.0 ), 135, 0, 360, Scalar( 0, 0, 255 ), 3, 8 );
ellipse( image, Point( 200, 200 ), Size( 100.0, 150.0 ), 180, 0, 360, Scalar( 255,255, 0 ), 3, 8 );
imshow("Image",image);
waitKey( 0 );
return(0);
}