How to display the final decision for face detection using opencv - c++

Question

I am a beginner of using opencv. I using opencv 2.4 with VS2013. I had develop face detection code and success but the decision made is from frame by frame. How can I made final decision by combining all the frame or frame averaging?? For example, when the total face detected is 90% detected, the final decision is 'FACE DETECTED' and vice versa.
Here is my code:
int main(int argc, char** argv)
{
CvCapture* capture;
capture = cvCaptureFromFile("C:/Users/user/Desktop/Face and Motion/45.avi");
//assert(capture != NULL); //terminate if capture is NULL
IplImage* frame;
while (true)
{
frame = cvQueryFrame(capture);
if (!frame)
break;
cvShowImage("original", frame); //show
CvMemStorage* storage = cvCreateMemStorage(0);
CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad("C:/opencv2410/sources/data/haarcascades/haarcascade_frontalface_alt.xml");
cvClearMemStorage(storage);
CvSeq* faces = cvHaarDetectObjects(frame, cascade, storage, 1.1, 4, 0, cvSize(40, 50));
CvRect* r;
if (faces) //change from (!faces) to (faces)
{
for (int i = 0; i < (faces ? faces->total : 0); i++)
{
r = (CvRect*)cvGetSeqElem(faces, i);
//cvRectangle(frame, cvPoint(100, 50), cvPoint(200, 200), CV_RGB(255, 0, 0), 5, 8);
cvRectangle(frame, cvPoint(r->x, r->y), cvPoint(r->x + r->width, r->y + r->height), CV_RGB(255, 0, 0));
cvShowImage("RESULTS", frame);
char c = cvWaitKey(1000);
}
}
else
{
cvShowImage("RESULT", frame);
}
printf("%d Face Found !\n", faces ? faces->total : 0);
if ((faces ? faces->total : 0) == 0)
{
printf("FACE NOT DETECTED !\n\n");
}
else
{
printf("FACE DETECTED !\n\n");
}
}
return (0);
}

Answer 1

you need two variables like
int frame_count = 0;
int detected_face_count = 0;
you should increase frame_count for every frame and increase detected_face_count when a face detected. finally detected_face_count / frame_count gives your desired value.
however, i did some corrections on your code (i could not test it)
changes explained by comments. i hope it will be useful.
int main(int argc, char** argv)
{
CvCapture* capture;
capture = cvCaptureFromFile("C:/Users/user/Desktop/Face and Motion/45.avi");
//assert(capture != NULL); //terminate if capture is NULL
IplImage* frame;
//you need two variables
int frame_count = 0;
int detected_face_count = 0;
// these lines should not be in the loop
CvMemStorage* storage = cvCreateMemStorage(0);
CvHaarClassifierCascade* cascade = (CvHaarClassifierCascade*)cvLoad("C:/opencv2410/sources/data/haarcascades/haarcascade_frontalface_alt.xml");
while (true)
{
frame = cvQueryFrame(capture);
if (!frame)
break;
frame_count++; // increase frame_count
cvShowImage("original", frame); //show
cvClearMemStorage(storage);
CvSeq* faces = cvHaarDetectObjects(frame, cascade, storage, 1.1, 4, 0, cvSize(40, 50));
CvRect* r;
for (int i = 0; i < (faces ? faces->total : 0); i++)
{
r = (CvRect*)cvGetSeqElem(faces, i);
//cvRectangle(frame, cvPoint(100, 50), cvPoint(200, 200), CV_RGB(255, 0, 0), 5, 8);
cvRectangle(frame, cvPoint(r->x, r->y), cvPoint(r->x + r->width, r->y + r->height), CV_RGB(255, 0, 0));
}
cvShowImage("RESULT", frame);
char c = cvWaitKey(1000);
printf("%d Face Found !\n", faces ? faces->total : 0);
if ((faces ? faces->total : 0) == 0)
{
printf("FACE NOT DETECTED !\n\n");
}
else
{
detected_face_count ++; // increase detected_face_count
printf("FACE DETECTED !\n\n");
}
}
if( (float)(detected_face_count / frame_count) > 0.89 )
{
printf("FACES DETECTED over %90 of frames!\n\n");
}
return (0);
}
as #Miki stated you should not use deprecated C api
take a look at the code below using C++ api (tested with OpenCV 3.1)
#include <opencv2/opencv.hpp>
using namespace cv;
using namespace std;
int main(int argc, char** argv)
{
VideoCapture capture("C:/Users/user/Desktop/Face and Motion/45.avi");
if(!capture.isOpened())
{
printf("Video file could not be opened !\n");
return -1;
}
Mat frame;
//you need two variables
int frame_count = 0;
int detected_face_count = 0;
// these lines should not be in the loop
CascadeClassifier cascade;
if( !cascade.load( "C:/opencv2410/sources/data/haarcascades/haarcascade_frontalface_alt.xml" ) )
{
cerr << "ERROR: Could not load classifier cascade" << endl;
return -1;
}
while (true)
{
capture >>frame;
if (frame.empty())
break;
frame_count++; // increase frame_count
imshow("original", frame); //show
vector<Rect> faces;
cascade.detectMultiScale(frame, faces,1.1, 4, 0, Size(40, 50));
for (int i = 0; i < faces.size(); i++)
{
rectangle(frame, faces[i], Scalar(0, 0, 255));
}
imshow("RESULT", frame);
char c = waitKey(10);
printf("%d Face Found !\n", faces.size());
if ( faces.size() == 0 )
{
printf("FACE NOT DETECTED !\n\n");
}
else
{
detected_face_count ++; // increase detected_face_count
printf("FACE DETECTED !\n\n");
}
}
printf("count of frames : %d \n", frame_count);
printf("count of frames has detected face : %d \n", detected_face_count);
printf("Face Found %d percent of frames!\n", (int)(100 * detected_face_count / frame_count));
if( (float)(detected_face_count / frame_count) > 0.89 )
{
printf("FACES DETECTED over %90 of frames!\n\n");
}
return (0);
}