opencv 如何使用鼠标事件不规则地选择图像区域?C/C++

I had a little attempt at this - it is probably not the cleanest code, but should give you some ideas.

#include <opencv2/opencv.hpp>
#include <iostream>

using namespace std;
using namespace cv;

// Globals
bool finished=false;
Mat img,ROI;
vector<Point> vertices;

void
CallBackFunc(int event,int x,int y,int flags,void* userdata)
{
   if(event==EVENT_RBUTTONDOWN){
      cout << "Right mouse button clicked at (" << x << ", " << y << ")" << endl;
      if(vertices.size()<2){
         cout << "You need a minimum of three points!" << endl;
         return;
      }
      // Close polygon
      line(img,vertices[vertices.size()-1],vertices[0],Scalar(0,0,0));

      // Mask is black with white where our ROI is
      Mat mask= Mat::zeros(img.rows,img.cols,CV_8UC1);
      vector<vector<Point>> pts{vertices};
      fillPoly(mask,pts,Scalar(255,255,255));
      img.copyTo(ROI,mask);
      finished=true;

      return;
   }
   if(event==EVENT_LBUTTONDOWN){
      cout << "Left mouse button clicked at (" << x << ", " << y << ")" << endl;
      if(vertices.size()==0){
         // First click - just draw point
         img.at<Vec3b>(x,y)=Vec3b(255,0,0);
      } else {
         // Second, or later click, draw line to previous vertex
         line(img,Point(x,y),vertices[vertices.size()-1],Scalar(0,0,0));
      }
      vertices.push_back(Point(x,y));
      return;
   }
}

int main()
{
   // Read image from file 
   img=imread("demo.jpg");

   // Check it loaded
   if(img.empty()) 
   { 
      cout << "Error loading the image" << endl;
      exit(1);
   }

   //Create a window
   namedWindow("ImageDisplay",1);

   // Register a mouse callback
   setMouseCallback("ImageDisplay",CallBackFunc,nullptr);

   // Main loop
   while(!finished){
      imshow("ImageDisplay",img);
      waitKey(50);
   }

   // Show results
   namedWindow("Result",1);
   imshow("Result",ROI);
   waitKey(5000);
}

在 main() 的开头我这样做:

setMouseCallback("ImageDisplay",CallBackFunc,nullptr);

void CallBackFunc(...)