用鼠标在窗口中画方形的程序

#include <cv.h>
#include <highgui.h>
void my_mouse_callback(int event, int x, int y, int flags, void* param);

CvRect box;
bool drawing_box = false;

void draw_box(IplImage *img, CvRect rect)
{
    cvRectangle(img, cvPoint(box.x, box.y), cvPoint(box.x + box.width, box.y + box.height), cvScalar(0xff, 0x00, 0x00));
}
int main()
{
    box = cvRect(-1, -1, 0, 0);
    IplImage *image = cvCreateImage(cvSize(200, 200), IPL_DEPTH_8U, 3);
    cvZero(image);
    IplImage *temp = cvCloneImage(image);
    cvNamedWindow("Box Example");
    cvSetMouseCallback("Box Example", my_mouse_callback, (void*)image);
    while (1)
    {
        cvCopyImage(image, temp);
        if (drawing_box) draw_box(temp, box);
        cvShowImage("Box Example", temp);
        char c = cvWaitKey(15);
        if (c == 27) break;
    }
    cvReleaseImage(&image);
    cvReleaseImage(&temp);
    cvDestroyWindow("Box Example");
    return 0;
}
void my_mouse_callback(int event, int x, int y, int flags, void* param)
{
    IplImage *image = (IplImage*)param;
    switch (event)
    {
    case CV_EVENT_MOUSEMOVE:{ //鼠标进行移动
        if (drawing_box)
        {
            box.width = x - box.x;
            box.height = y - box.y;
        }
    }
    break;
    case CV_EVENT_LBUTTONDOWN:
    {
        drawing_box = true;
        box = cvRect(x, y, 0, 0); //确定当前矩形的左上角 width和height不确定
    }
    break;
    case CV_EVENT_MBUTTONUP:{ //确定一个矩形
        drawing_box = false;
        if (box.width < 0) //设定矩形以左上角为基础 
        {
            box.x += box.width;
            box.width *= -1;
        }
        if (box.height < 0)
        {
            box.y += box.height;
            box.height *= -1;
        }
        draw_box(image, box);
    }
    break;
    }
}