使用opencv实现在一张图片上按下鼠标左键并随着鼠标的移动画一个矩形

具体实现的程序如下：

#include 
#include 

void on_MouseHandle(int event, int x, int y, int flags, void* param);	//鼠标响应函数

cv::Mat frame;			//定义一个全局的Mat变量，用于存储图像

int main(int argc, char** argv) 
{
	cv::namedWindow("picture", cv::WINDOW_NORMAL);
	cv::setMouseCallback("picture", on_MouseHandle);	//关联鼠标响应函数

	frame = cv::imread("other9.jpg");	//读取图片
	imshow("picture", frame);  //显示图片
	cv::waitKey(0);            //直到有按键按下
	return 0;
}

void on_MouseHandle(int event, int x, int y, int flags, void* param)
{
	static cv::Point pt1, pt2;
	static int start = 0;
	cv::Mat img;

	frame.copyTo(img);   //这样复制两个变量不会使用同一幅图像
	switch (event)
	{
		case cv::EVENT_LBUTTONDOWN:		//左键按下消息
		{
			start = 1;
			pt1 = cv::Point(x, y);
			std::cout << "start: (" << pt1.x << ", " << pt1.y << ")" << std::endl;
			break;
		}
		case cv::EVENT_MOUSEMOVE:		//鼠标移动事件
		{
			pt2 = cv::Point(x, y);
			if (start == 1)
			{
				cv::rectangle(img, pt1, pt2, cv::Scalar(0, 0, 255), 10, 80, 0);
				imshow("picture", img);  //显示当前已画矩形的图片
			}
			break;
		}
		case cv::EVENT_LBUTTONUP:		//鼠标左键弹起事件
		{
			start = 0;
			pt2 = cv::Point(x, y);
			std::cout << "end: (" << pt2.x << ", " << pt2.y << ")" << std::endl;
			break;
		}
	}
}