旋转矩形的四个角通过矩形的中心点和角度在图像上找到

int rectangle2(Mat& src,vector& out_points, Point2f center, double angle, double w_length,double h_length, Scalar color, int thickness)
参数：
Mat& src 输入并输出图片
vector& out_points 得到四个点
Point2f center 矩形中心点
double angle 矩形角度
double w_length 一半的矩形宽度
double h_length 矩形长的一半
Scalar color 颜色
int thickness 线宽 -1为填充**

int rectangle2(Mat& src,vector& out_points, Point2f center, double angle, double w_length,double h_length, Scalar color, int thickness)      Mat& src  输入并输出图片     vector& out_points    得到四个点     Point2f center   矩形中心点     double angle     矩形角度     double w_length  一半的矩形宽度     double h_length  半长矩形     Scalar color     颜色     int thickness    线宽     -1为填充** 

int rectangle2(Mat& src,vector<Point2f>& out_points, Point2f center, double angle, double w_length,double h_length, Scalar color, int thickness) { 
             if (src.empty())         return -1;      angle = -angle;     vector<Point2f> before_points(4),later_points(4);     double cosA = cos(angle / (180.0 / CV_PI));     double sinA = sin(angle / (180.0 / CV_PI));     //左上，右上，右下，左下     before_points[0] = Point(center.x - w_length, center.y - h_length);     before_points[1] = Point(center.x + w_length, center.y - h_length); before_points[2] = Point(center.x + w_length, center.y + h_length); before_points[3] = Point(center.x - w_length, center.y + h_length); //带角度的矩形四角点 later_points[0].x = (before_points[0].x - center.x) * cosA - (before_points[0].y - center.y) * sinA + center.x; later_points[0].y = (before_points[0].x - center.x) * sinA + (before_points[0].y - center.y) * cosA + center.y; later_points[1].x = (before_points[1].x - center.x) * cosA - (before_points[1].y - center.y) * sinA + center.x; later_points[1].y = (before_points[1].x - center.x) * sinA + (before_points[1].y - center.y) * cosA + center.y; later_points[2].x = (before_points[2].x - center.x) * cosA - (before_points[2].y - center.y) * sinA + center.x; later_points[2].y = (before_points[2].x - center.x) * sinA + (before_points[2].y - center.y) * cosA + center.y; later_points[3].x = (before_points[3].x - center.x) * cosA - (before_points[3].y - center.y) * sinA + center.x; later_points[3].y = (before_points[3].x - center.x) * sinA + (before_points[3].y - center.y) * cosA + center.y; int thicknes = thickness; if (thickness == -1) thicknes = 1; line(src, later_points[0], later_points[1], color, thicknes); line(src, later_points[1], later_points[2], color, thicknes); line(src, later_points[2], later_points[3], color, thicknes); line(src, later_points[3], later_points[0], color, thicknes); out_points = later_points; if (thickness == -1) { 
          Mat mask = Mat::zeros(src.size(), CV_8U); line(mask, later_points[0], later_points[1], Scalar(255), thicknes); line(mask, later_points[1], later_points[2], Scalar(255), thicknes); line(mask, later_points[2], later_points[3], Scalar(255), thicknes); line(mask, later_points[3], later_points[0], Scalar(255), thicknes); vector<vector<Point>> contours; vector<Vec4i> hierarchy; findContours(mask, contours, hierarchy, RETR_TREE, CHAIN_APPROX_NONE); drawContours(src, contours, 0, color, -1); } return 0; }