opencv用鼠标在窗口中画方形的程序

#include <iostream>
#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);
if(cvWaitKey(15)==27) break;
}
cvReleaseImage(&image);
cvReleaseImage(&temp);
cvDestroyWindow("Box Example");
}

void my_mouse_callback(int event, int x, int y, int flags, void* param)
{
IplImage* image = (IplImage*) param;
switch( event )
{
case CV_EVENT_MOUSEMOVE:
{
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);
}
break;
case CV_EVENT_LBUTTONUP:
{
drawing_box = false;
if(box.width<0)
{
box.x+=box.width;
box.width*=-1;
}
if(box.height<0)
{
box.y+=box.height;
box.height*=-1;
}
draw_box(image, box);
}
break;
}
}