face detection using HAAR classifier - opencv

Question

Iam working on face detection in openCV with HAAR classifier. Here is my code
#include "stdafx.h"
#include <opencv2\objdetect\objdetect.hpp>
#include <opencv2\highgui\highgui.hpp>
#include <opencv2\imgproc\imgproc.hpp>
#include <opencv\cv.h>
#include <iostream>
#include <stdio.h>
using namespace std;
using namespace cv;
void detectAndDisplay(Mat frame);
String face_cascade_name = "haarcascade_frontalface_alt.xml";
String eyes_cascade_name = "haarcascade_eye_tree_eyeglasses.xml";
CascadeClassifier face_cascade;
CascadeClassifier eye_cascade;
string window_name = "Capture- Face detection";
int _tmain(int argc, _TCHAR* argv[])
{
Mat frame = imread("C:/Users/Public/Pictures/Sample Pictures/lena.png");
imshow("original picture", frame);
if (face_cascade.load(face_cascade_name))
{
cout << "\n Error loading " << endl;
}
if (eye_cascade.load(eyes_cascade_name))
{
cout << "\n Error Loading " << endl;
}
if (!frame.empty())
{
detectAndDisplay(frame);
}
waitKey(0);
return 0;
}
void detectAndDisplay(Mat frame)
{
vector<Rect>faces;
imshow("lena.png", frame);
Mat frame_gray;
cvtColor(frame, frame_gray, CV_BGR2GRAY);
equalizeHist(frame_gray, frame_gray);
imshow("Gray Color Image", frame_gray);
face_cascade.detectMultiScale(frame_gray, faces, 1.1, 2, 0 | CV_HAAR_SCALE_IMAGE, Size(20, 20));
int k = faces.size();
for (size_t i = 0; i <faces.size(); i++)
{
Point center(faces[i].x + faces[i].width*0.5, faces[i].y + faces[i].height*0.5);
ellipse(frame, center, Size(faces[i].width*0.5, faces[i].height*0.5), 0, 0, 360, Scalar(255, 0, 0));
Mat faceROI = frame_gray(faces[i]);
vector<Rect>eyes;
eye_cascade.detectMultiScale(faceROI, eyes, 1.1, 2, 0 | CV_HAAR_SCALE_IMAGE, Size(30, 30));
for (int j = 0; j < eyes.size(); j++)
{
Point center(faces[i].x + eyes[j].x + eyes[j].width*0.5, faces[i].y + eyes[j].y + eyes[j].height*0.5);
int radius = cvRound((eyes[j].width + eyes[j].height)*0.25);
circle(frame, center, radius, Scalar(0, 0,255), 4, 8, 0);
}
}
imshow(window_name, frame);
}
Here My code is not working. face is not being detected. iam trying get int k=faces.size() which is getting '0' value. what could be the possible error.

Answer 1

That is because your if-condition to load the cascade is not logic:
Yours is:
if (face_cascade.load(face_cascade_name))
{
cout << "\n Error loading " << endl;
}
if (eye_cascade.load(eyes_cascade_name))
{
cout << "\n Error Loading " << endl;
}
But it should be:
if (!face_cascade.load(face_cascade_name))
{
cout << "\n Error loading " << endl;
}
if (!eye_cascade.load(eyes_cascade_name))
{
cout << "\n Error Loading " << endl;
}
You forget the '!' in the conditions.

Answer 2

face_cascade.load(face_cascade_name) obviously returns FALSE when classifier successfully loaded. You can find it in one of the samples provided with OpenCV library facedetect.cpp
This is why you don't see that the loading process failed and you provided wrong path to haarcascade file.