Mat rotated_full_map_image;
Point2f src_center(full_map_image.cols/2.0F, full_map_image.rows/2.0F);
Mat rot_mat = getRotationMatrix2D(src_center, angle, 1.0);
warpAffine(full_map_image, rotated_full_map_image, rot_mat, full_map_image.size());

Point rotated_centre;
Point2f p(some_x,some_y);
rotated_centre.x = rot_mat.at<double>(0,0)*p.x + rot_mat.at<double>(0,1)*p.y + rot_mat.at<double>(0,2);
rotated_centre.y = rot_mat.at<double>(1,0)*p.x + rot_mat.at<double>(1,1)*p.y + rot_mat.at<double>(1,2);