OpenCV [c++]画矩形框截图显示ROI并保存 以及 滚动条视频播放控制

#include 
#include
using namespace std;
using namespace cv;


Mat srcImg, temp, ROI;
Point p;
bool flag =false;  
void onMouse(int event, int x, int y, int flags, void* param)
{
    switch (event)
    {
    case EVENT_LBUTTONDOWN:  //鼠标左键按下
        cout << "EVENT_LBUTTONDOWN" << endl;
        p.x = x;
        p.y = y;
        flag = true;
        break;
    case EVENT_MOUSEMOVE:    //鼠标移动
        if (flag==true)
        {
            temp.copyTo(srcImg);
            rectangle(srcImg, p, Point(x, y), Scalar(0,255,0), 2, 8);
            
        }
        break;
    case EVENT_LBUTTONUP:    //鼠标左键抬起
        flag = false;
        ROI = temp(Rect(p.x, p.y, x - p.x, y - p.y));
        imshow("ROI", ROI);
        imwrite("ROI.bmp", ROI);
        break;
    default:
        break;
    }

}
int main()
{
    srcImg = imread("1.png");
    temp = srcImg.clone();
    namedWindow("Window", WINDOW_NORMAL);
    setMouseCallback("Window", onMouse, 0);
    while (1)
    {
        if (waitKey(20) == 27)
        {
            break;
        }
        imshow("Window", srcImg);
        
    }
}