openCV 用鼠标在窗口中画方形

// chapter.cpp : 定义控制台应用程序的入口点。
//

#include "stdafx.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(0,0,255));
}

int _tmain(int argc, _TCHAR* argv[])
{
	box=cvRect(-1,-1,0,0);//初始化box
	IplImage *image=cvCreateImage(cvSize(200,200),IPL_DEPTH_8U,3);
	cvZero(image);
	IplImage * temp=cvCloneImage(image);

	cvNamedWindow("Box",0);
	
	cvSetMouseCallback("Box",my_mouse_callback,(void *)image);//将回调函数注册到openCV
	while(1){
		cvCopy(image,temp);
		if(drawing_box) draw_box(temp,box);
		cvShowImage("Box",temp);
		if(cvWaitKey(15)==27) break;
	}
	cvReleaseImage(&image);
	cvReleaseImage(&temp);
	cvDestroyWindow("Box");
	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:{
			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;
	}
}