用鼠标在窗口中画方形

//用鼠标在窗口中画方形
//作者：sandy
//时间：2015-10-7

//user can draw boxes on the screen
#include <cv.h>
#include <highgui.h>
using namespace std;

CvRect box;
bool drawing_box=false;

//定义一个回调函数
//define our callback which we will install for mouse event
//
void my_mouse_callback(int event ,int x,int y,int flags,void* param);

//实现把方形画在一幅画上的小程序
//A little subroutine to draw a box into an image
//
void draw_box(IplImage* img ,CvRect rect);

int main(int argc,char* argv[]){

box=cvRect(-1,-1,0,0);//(x,y,width,height)

IplImage* image=cvCreateImage(cvSize(400,400),IPL_DEPTH_8U,3);//创建一个图像（画板）
cvZero(image);//将数组中的所有通道的元素的值都设置为0.
IplImage* temp=cvCloneImage(image);//image克隆到temp

cvNamedWindow("mouse_rect_window");//定义一个视窗

//在opencv中注册回调函数,传入图像参数，以便特定窗口被触发鼠标事件后，opencv可以正确调用
//
cvSetMouseCallback("mouse_rect_window",my_mouse_callback,(void*) image);//触发窗口为：mouse_rect_window，触发调用函数为：my_mouse_callback,传给触发调用函数的void * param值为(void*) image

//The main program loop.here we copy the working image to the 'temp' image,
//and if the user is drawing , then put the currently contemplated box onto the
//temp image.Display the temp image,and wait 15ms for a keystroke,then repeat...
//
while(1){
cvCopyImage(image,temp);//把image复制到temp中
if(drawing_box) draw_box(temp,box);
cvShowImage("mouse_rect_window",temp);

if(cvWaitKey(15)==27) break;
}

cvReleaseImage(&image);
cvReleaseImage(&temp);
cvDestroyWindow("mouse_rect_window");
}

//鼠标响应事件
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;
//cout<<x<<','<<y<<endl;
//cout<<box.x<<','<<box.y<<endl;
}
}
break;
case CV_EVENT_LBUTTONDOWN:{
drawing_box=true;
box=cvRect(x,y,0,0);//起点坐标，宽，高
//cout<<x<<','<<y<<endl;
//cout<<box.x<<','<<box.y<<endl;
}
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;

}
}
//实现把方形画在一幅画上的小程序
//A little subroutine to draw a box into an image
//
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, 120, 255)//画线的颜色
);
}