opencv利用滑鼠擷取映像的像素值

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;      }