OpenCV实现鼠标框选并显示框选区域

#include <cv.h>
#include <highgui.h>
#include <stdio.h>
 
IplImage* src = 0; 
IplImage* tmp = 0; 
IplImage* tmp1 = 0;
IplImage* org = 0;
void on_mouse( int event, int x, int y, int flags, void* ustc)
{
 static CvPoint pre_pt = {-1,-1};
 static CvPoint cur_pt = {-1,-1};
 CvFont font;
 cvInitFont(&font, CV_FONT_HERSHEY_SIMPLEX, 0.5, 0.5, 0, 1, CV_AA);//初始化字体
 char temp[16];
 
 if( (event == CV_EVENT_LBUTTONDOWN)&&(flags) )//鼠标左键按下时
 { 
 sprintf(temp,"(%d,%d)",x,y);//格式化字符串
 pre_pt = cvPoint(x,y);//获取当前点坐标值
 cvPutText(src,temp, pre_pt, &font, cvScalar(0,0, 0, 255));//在图像是打印字符
 cvCircle( src, pre_pt, 2,cvScalar(255,0,0,0) ,CV_FILLED, CV_AA, 0 );//在图像上画圆
 cvShowImage( "src", src );
 //cvCopy(src,tmp);//这句有没有，就是单目标和多目标的问题
 }
 else if( (event == CV_EVENT_MOUSEMOVE) && (flags & CV_EVENT_LBUTTONDOWN))
 {//鼠标移动并且鼠标左键按下
 sprintf(temp,"(%d,%d)",x,y);//格式化字符串
 cur_pt = cvPoint(x,y);//获取当前点坐标值 
 cvPutText(src,temp, cur_pt, &font, cvScalar(0,0, 0, 255));//在图像是打印字符
 cvRectangle(src, pre_pt, cur_pt, cvScalar(0,255,0,0), 2, 8, 0 );//在图像上画矩形
 cvShowImage( "src", src );
 cvCopy(tmp,src);//将img复制到临时图像tmp上，用于实时显示
 }
 else if( event == CV_EVENT_LBUTTONUP )
 {//鼠标左键弹起
 sprintf(temp,"(%d,%d)",x,y);//字体格式化
 cur_pt = cvPoint(x,y);//获取当前点坐标值 
 cvPutText(src,temp, cur_pt, &font, cvScalar(0,0, 0, 255));//在图像是打印字符
 cvCircle( src, cur_pt, 2,cvScalar(255,0,0,0) ,CV_FILLED, CV_AA, 0 );//在图像上画圆
 cvRectangle( src, pre_pt, cur_pt, cvScalar(0,255,0,0), 2, 8, 0 );//在图像上画矩形
 cvShowImage( "src", src );
 
 /******************************************************************/
 int width=abs(pre_pt.x-cur_pt.x); //两点横坐标差 
    int height=abs(pre_pt.y-cur_pt.y); //两点纵坐标差 
    if(width==0 || height==0) 
    { //两者中有一个为零时销毁窗口
      cvDestroyWindow("dst"); 
      return; 
    } 
    tmp1 = cvCreateImage(cvSize(width,height),org->depth,org->nChannels); 
    CvRect rect; 
    if(pre_pt.x<cur_pt.x && pre_pt.y<cur_pt.y) 
    { 
      rect=cvRect(pre_pt.x,pre_pt.y,width,height); 
    } 
    else if(pre_pt.x>cur_pt.x && pre_pt.y<cur_pt.y) 
    { 
      rect=cvRect(cur_pt.x,pre_pt.y,width,height); 
    } 
    else if(pre_pt.x>cur_pt.x && pre_pt.y>cur_pt.y) 
    { 
      rect=cvRect(cur_pt.x,cur_pt.y,width,height); 
    } 
    else if(pre_pt.x<cur_pt.x && pre_pt.y>cur_pt.y) 
    { 
      rect=cvRect(pre_pt.x,cur_pt.y,width,height); 
    } 
    cvSetImageROI(org,rect);//设置图像的感兴趣区域 
    cvCopy(org,tmp1); //将感兴趣区域复制到tmp1 
    cvResetImageROI(org);//释放图像的感兴趣区域 
    cvDestroyWindow("dst");//销毁上次的显示图像 
    cvNamedWindow("dst",1);//新建窗口 
    cvShowImage("dst",tmp1); //显示感兴趣的图像 
    cvSaveImage("dst.jpg",tmp1); //保存感兴趣图像 
/******************************************************************/
 }
}
int main()
{
 src=cvLoadImage("lena.jpg",1);//读入图像
 tmp=cvCloneImage(src);//复制图像到临时图像上 
 org=cvCloneImage(src);//保存原始图像 
 cvNamedWindow("src",1);//新建窗口
 cvSetMouseCallback( "src", on_mouse, 0 );//注册鼠标响应回调函数
 
 cvShowImage("src",src);//显示图像
 cvWaitKey(0);//等待按键按下 
 cvDestroyAllWindows();//销毁所有窗口
 cvReleaseImage(&src);//释放图像
 cvReleaseImage(&tmp);//释放图像
 return 0;
}