Multiple Face Detection - opencv

Question

I have a code in OpenCV (in C++) which uses "haarcascade_mcs_upperbody.xml" to detect upper body.
It detects single upper body. How can I make it detect multiple upper bodies.
I think CV_HAAR_FIND_BIGGEST_OBJECT is detecting only the biggest object. But I am not knowing how to solve this issue
The code goes like this:
int main(int argc, const char** argv)
{
CascadeClassifier body_cascade;
body_cascade.load("haarcascade_mcs_upperbody.xml");
VideoCapture captureDevice;
captureDevice.open(0);
Mat captureFrame;
Mat grayscaleFrame;
namedWindow("outputCapture", 1);
//create a loop to capture and find faces
while(true)
{
//capture a new image frame
captureDevice>>captureFrame;
//convert captured image to gray scale and equalize
cvtColor(captureFrame, grayscaleFrame, CV_BGR2GRAY);
equalizeHist(grayscaleFrame, grayscaleFrame);
//create a vector array to store the face found
std::vector<Rect> bodies;
//find faces and store them in the vector array
body_cascade.detectMultiScale(grayscaleFrame, faces, 1.1, 3,
CV_HAAR_FIND_BIGGEST_OBJECT|CV_HAAR_SCALE_IMAGE, Size(30,30));
//draw a rectangle for all found faces in the vector array on the original image
for(int i = 0; i < faces.size(); i++)
{
Point pt1(bodies[i].x + bodies[i].width, bodies[i].y + bodies[i].height);
Point pt2(bodies[i].x, bodies[i].y);
rectangle(captureFrame, pt1, pt2, cvScalar(0, 255, 0, 0), 1, 8, 0);
}
//print the output
imshow("outputCapture", captureFrame);
//pause for 33ms
waitKey(33);
}
return 0;
}

Answer 1

It seems there is some inconsistency in your code, since face_cascade is not defined anywhere, but I assume its type is CascadeClassifier.
detectMultiScale stores all detected objects in the faces vector. Are you sure it contains only one object?
Try removing the CV_HAAR_FIND_BIGGEST_OBJECT flag, because you want all objects to be detected, and not only the biggest one.
Also, make sure you set the minSize and maxSize parameters correctly (see documentation), since those parameters determine the minimal and maximal detectable object sizes.