OpenCV怎么画箭头(How to draw an arrow)

转自：http://tmjfzy.blog.163.com/blog/static/664470252012225101017794/

示例代码：

   1: #include 

   2: #include 

   3: #pragma comment(lib, "opencv_core231d.lib")

   4: #pragma comment(lib, "opencv_highgui231d.lib")

   5: #pragma comment(lib, "opencv_imgproc231d.lib")

   6: using namespace std;

   7: using namespace cv;

   8:  

   9: void drawArrow(cv::Mat& img, cv::Point pStart, cv::Point pEnd, int len, int alpha,

  10:     cv::Scalar& color, int thickness = 1, int lineType = 8);

  11:  

  12: int main()

  13: {         

  14:     Mat M(400, 400, CV_8UC3, Scalar(0, 0, 0));       

  15:     Point pStart(380, 100), pEnd(100, 250);       

  16:     Scalar lineColor(0, 255, 255);    

  17:     drawArrow(M, pStart, pEnd, 10, 45, lineColor);    

  18:     pStart = Point(100, 100);    

  19:     pEnd = Point(320, 190);     

  20:     lineColor = Scalar(0, 0, 255);    

  21:     drawArrow(M, pStart, pEnd, 25, 30, lineColor, 2, CV_AA); 

  22:     pStart = Point(200, 420);    

  23:     pEnd = Point(370, 170);    

  24:     lineColor = Scalar(255, 0, 255); 

  25:     drawArrow(M, pStart, pEnd, 17, 15, lineColor, 1, 4);   

  26:     imshow("draw arrow", M);    

  27:     waitKey();     

  28:     return 0;

  29: }

  30:  

  31: void drawArrow(cv::Mat& img, cv::Point pStart, cv::Point pEnd, int len, int alpha,             

  32:     cv::Scalar& color, int thickness, int lineType)

  33: {    

  34:     const double PI = 3.1415926;    

  35:     Point arrow;    

  36:     //计算 θ 角（最简单的一种情况在下面图示中已经展示，关键在于 atan2 函数，详情见下面）   

  37:     double angle = atan2((double)(pStart.y - pEnd.y), (double)(pStart.x - pEnd.x));  

  38:     line(img, pStart, pEnd, color, thickness, lineType);   

  39:     //计算箭角边的另一端的端点位置（上面的还是下面的要看箭头的指向，也就是pStart和pEnd的位置） 

  40:     arrow.x = pEnd.x + len * cos(angle + PI * alpha / 180);     

  41:     arrow.y = pEnd.y + len * sin(angle + PI * alpha / 180);  

  42:     line(img, pEnd, arrow, color, thickness, lineType);   

  43:     arrow.x = pEnd.x + len * cos(angle - PI * alpha / 180);     

  44:     arrow.y = pEnd.y + len * sin(angle - PI * alpha / 180);    

  45:     line(img, pEnd, arrow, color, thickness, lineType);

  46: }

运行结果

 

原理

如图