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#include
   
    #include
    
     using namespace std;using namespace cv;Point pt;bool flag = false;Mat ROI;Mat img = imread("E:\\OpenCV\\images\\fqy2.jpg");//原图片Mat src = img.clone();//用于出现多个矩形叠加void OnChange(int event, int x, int y, int flags, void *param) {
   	Mat &img = *(Mat *)param;	if (event == 1 && flags == 1) {
   //左键点击		flag = true;		pt.x = x;		pt.y = y;	}	else if (event == 0 && flags == 1) {
   	//左键拖动，注意区别鼠标移动和左键拖动的区别，这里改成鼠标移动代码无法正常运行		if (flag) {
   			src.copyTo(img);			rectangle(img, pt, Point(x, y), Scalar(255, 0, 0), 2);			imshow("pic", img);		}	}	else if (event == 4) {
   //左键弹起		flag = false;		ROI = src(Rect(pt.x, pt.y, x - pt.x, y - pt.y));		imshow("pic", ROI);		imwrite("E:\\OpenCV\\images\\fqy1.jpg", ROI);//输出路径	}}int main(){
   	namedWindow("pic", WINDOW_AUTOSIZE);	setMouseCallback("pic", OnChange, &img);	imshow("pic", img);	waitKey(0);}
    
   

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