鼠标事件

#include <opencv2/core.hpp>
#include <opencv2/imgproc.hpp>
#include <opencv2/highgui.hpp>
#include <vector>
#include <iostream>
#include <math.h>

cv::Mat source;
cv::Mat bakSource;
cv::Point center;
void drawCircle(int action, int x, int y, int flags, void *userdata) {
    switch (action) { 
    case cv::EVENT_LBUTTONDOWN:
        center.x = x;
        center.y = y; 
        
        std::cout << "左键点下" << std::endl;
        break;
    case cv::EVENT_LBUTTONUP:
        std::cout << "左键弹起" << std::endl;
        break;
    case cv::EVENT_MOUSEMOVE:
        if (flags == cv::EVENT_FLAG_LBUTTON) {
            int dx = x - center.x;
            int dy = y - center.y;
            int r = sqrt(dx*dx + dy*dy);
            bakSource.copyTo(source);
            cv::circle(source, center, 1, cv::Scalar(0, 0, 255), 2);
            cv::circle(source, center, r, cv::Scalar(0, 255, 0), 2);
            cv::imshow("鼠标事件", source);
        }
        break;
    }
}
int main()
{
    source = cv::imread("test.png");
    source.copyTo(bakSource);
    cv::namedWindow("鼠标事件"); 
    cv::setMouseCallback("鼠标事件", drawCircle);
    cv::imshow("鼠标事件", source);
    cv::waitKey();
　　 cv::destroyAllWindows();
    return 0;
}

OpenCV使用setMouseCallback设置鼠标事件回调函数,回调函数void functionname(int action, int x, int y, int flags, void *userdata)

action：表示鼠标的事件类型

x,y:表示当前鼠标相对屏幕的坐标

flags:当前鼠标的按键状态

userdata:用户数据

上面代码实现了左键按下并拖动鼠标绘制一个圆圈