Capturing the frame when the Object is detected - c++

Question

i have the following code :
#include <iostream>
#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/objdetect/objdetect.hpp>
#include <opencv2/imgproc/imgproc.hpp>
using namespace std;
using namespace cv;
String object_cascade_name = "haarcascade_frontalface_alt.xml";
CascadeClassifier object_cascade;
string window_name = "Capture - detector";
int main( void )
{
VideoCapture capture;
Mat frame;
std::vector<Rect> objects;
Mat frame_gray;
if( !object_cascade.load( object_cascade_name ) ){ std::cout << "ERROR: Cascade not loaded!\n" ; return -1; };
capture.open( 0 );
if( capture.isOpened() ){
for(;;){
capture >> frame;
capture.retrieve(frame);
//-- 3. Apply the classifier to the frame
if( !frame.empty() ){
// Start
cvtColor( frame, frame_gray, COLOR_BGR2GRAY );
equalizeHist( frame_gray, frame_gray );
//-- Detect Object
object_cascade.detectMultiScale( frame_gray, objects, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE, Size(30, 30) );
for( size_t i = 0; i < objects.size(); i++ ){
Point pt1 = Point( objects[i].x, objects[i].y );
Point pt2 = Point( objects[i].x + objects[i].width, objects[i].y + objects[i].height );
rectangle( frame, pt1, pt2, Scalar( 34, 92, 241 ), 2, 8, 0 );
Mat faceROI = frame_gray( objects[i] );
}
//-- Show what you got
imshow( window_name, frame );
// End
}
else{ std::cout << "ERROR: frame.empty returns 1!"; break; }
int c = waitKey(10);
if( (char)c == 'c' ) { break; }
}
}
return 0;
}
which plays a video from the build-in webcam and detect faces, my idea is that i want the video to stop when an object -face- is detected, then display a window contains the detected object only from the last frame.