鼠标（画矩形事件）—不怎么样

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

#define WINDOW_NAME "鼠标事件窗口"

using namespace std;
using namespace cv;

Rect g_rectangle;
bool g_bDrawingBox = false;
RNG g_rng(12345);

void DrawRectangle(Mat &img, Rect box)
{
    rectangle(img, box.tl(), box.br(), Scalar(g_rng.uniform(0, 255), g_rng.uniform(0, 255), g_rng.uniform(0, 255)));
}

/*注意：不能在毁掉函数中写入未初始化的矩阵类，所以需要用时，需要写一个标志位，然后再在while(1)循环内使用*/
void onMouse(int event, int x, int y, int flag, void *param)
{
    Mat &img = *(cv::Mat*)param;

    switch (event)
    { 
        //移动鼠标的时候
    case CV_EVENT_MOUSEMOVE:
    {
                               if (g_bDrawingBox)
                               {
                                   g_rectangle.width = x - g_rectangle.x;
                                   g_rectangle.height = y - g_rectangle.y;
                               }
    }
        break;
        //点击鼠标左键时
    case CV_EVENT_LBUTTONDOWN:
    {
                                 g_bDrawingBox = true;
                                 g_rectangle = Rect(x, y, 0, 0);
    }
        break;
        //松开鼠标左键时
    case CV_EVENT_LBUTTONUP:
    {
                               g_bDrawingBox = false;

                               DrawRectangle(img, g_rectangle);
    }
        break;
    }
}

int main()
{
    Mat srcImage(600, 800, CV_8UC3);
    Mat tempImage;

    srcImage.copyTo(tempImage);

    srcImage = Scalar::all(0);

    namedWindow(WINDOW_NAME);
    setMouseCallback(WINDOW_NAME, onMouse, (void *)&srcImage);

    while (1)
    {
        srcImage.copyTo(tempImage);

        if (g_bDrawingBox)
            DrawRectangle(tempImage, g_rectangle);

        imshow(WINDOW_NAME, tempImage);

        if(waitKey(10) == 27)
            break;

        /*DrawRectangle(srcImage, g_rectangle);
        imshow(WINDOW_NAME, srcImage);
        if (waitKey(10) == 27)
            break;*/
    }

    return 0;
}