opencv利用鼠标获取图像的像素值

void mouseHandler(int event, int x,int y ,int flags,void *p)  
{  
    IplImage *img0, *img1;  
    img0=(IplImage*)p;  
    img1=cvCloneImage(img0);  
   CvFont font;  
    uchar *ptr;  
    char label[20];  
    cvInitFont (&font,CV_FONT_HERSHEY_PLAIN,0.8,0.8,0,1,8);  
   if(event==CV_EVENT_LBUTTONDOWN)  
   {  
       ptr=cvPtr2D(img1, y,x,NULL);  
       sprintf(label, "(%d, %d, %d)",ptr[0], ptr[1], ptr[2]);  
       cvRectangle(img1, cvPoint(x,y-12),cvPoint(x+100, y+4),  
       CV_RGB(255,0,0),CV_FILLED, 8,0);  
        cvPutText(img1,label,cvPoint(x,y),&font,CV_RGB(255,255,255) );  
        cvShowImage("src",img1);  
    }  
}  
  
int main()  
{  
    IplImage *src;  
    src=cvLoadImage("e://kankan//fish.jpg");  
    assert(src);  
     cvNamedWindow("src", 1);  
    cvSetMouseCallback("src", mouseHandler, (void*)src);  
    mouseHandler(0,0,0,0,src);  
    cvShowImage("src",src);  
    cvWaitKey(0);  
    return 0;  
  
  
}void mouseHandler(int event, int x,int y ,int f