Real-time face detection in OpenCV - opencv

Question

I am trying to write some simple real time face detection code, but somehow it doesn't work. (I tried face detection code on an image and it works but with the code below i get a grey image onscreen and the code fails)
here is the code i have tried (it prints 'face detected!' one time to the output window)
CvHaarClassifierCascade *cascade;
CvMemStorage *storage;
char *face_cascade="haarcascade_frontalface_alt2.xml";
CvRect* r;
const CvArr* img_size;
IplImage *grayscale;
void detectFacialFeatures( IplImage *img)
{
grayscale = cvCreateImage(cvGetSize(img), 8, 1);
cvCvtColor(img, grayscale, CV_BGR2GRAY);
CvMemStorage* storage=cvCreateMemStorage(0);
cvClearMemStorage( storage );
cvEqualizeHist(grayscale, grayscale);
cascade = ( CvHaarClassifierCascade* )cvLoad( face_cascade, 0, 0, 0 );
CvSeq* faces = cvHaarDetectObjects(grayscale, cascade, storage, 1.1, 3, CV_HAAR_DO_CANNY_PRUNING, cvSize( 50, 50 ) );
if(faces)
{
printf("face detected!");
r = ( CvRect* )cvGetSeqElem( faces, 0 );
cvRectangle( img,cvPoint( r->x, r->y ),cvPoint( r->x + r->width, r->y + r->height ), CV_RGB( 255, 0, 0 ), 1, 8, 0 );
}
}
int _tmain(int argc, _TCHAR* argv[])
{
int c;
IplImage* color_img;
CvCapture* cv_cap = cvCreateCameraCapture(0);
cvSetCaptureProperty(cv_cap, CV_CAP_PROP_FRAME_WIDTH, 640);
cvSetCaptureProperty(cv_cap, CV_CAP_PROP_FRAME_HEIGHT, 480);
cvNamedWindow("Video",1); // create window
for(;;) {
color_img = cvQueryFrame(cv_cap); // get frame
if(color_img==0)
break;
cvFlip(color_img, 0, 1); //mirror image
detectFacialFeatures(color_img);
cvShowImage("Video", color_img); // show frame
c = cvWaitKey(10); // wait 10 ms or for key stroke
if(c == 27)
break; // if ESC, break and quit
}
/* clean up */
cvReleaseCapture( &cv_cap );
cvDestroyWindow("Video");
}

Answer 1

Try without calling functions cvFlip and cvEqualizeHistogram.
Look at(just use cvShowImage) result of each operation(cvFlip, cvCvtColor, cvEqualizeHistogram) - it's possible that result of one of these operations is gray image.
You don't have to load haar classifier each time you try to find a face - load it at the beginning. Operations on files are slow so it should makes you code faster.