Mat image(200, 200, CV_8UC3, Scalar(0));  
RotatedRect rRect = RotatedRect(Point2f(100,100), Size2f(100,50), 30);  
Point2f vertices[4];  
rRect.points(vertices);  
for (int i = 0; i < 4; i++)  
    line(image, vertices[i], vertices[(i+1)%4], Scalar(0,255,0));  
Rect brect = rRect.boundingRect();  
rectangle(image, brect, Scalar(255,0,0));  
imshow("rectangles", image);