OpenCV DetectMultiScale在C ++中不起作用

Question

I have the following code to load an image and compare to list of images trying to recognize matched faces. The call to DetectMultiScale returns a vector of size 0.

void UniCoffeeShop::Purchase (string customerImg){
vector <string> info;
Mat OriginalImg;
vector <Rect> faces;
Mat ImgGray;
Mat Img=imread("customers/"+customerImg+".tiff", CV_LOAD_IMAGE_COLOR);


cvtColor(Img,ImgGray,CV_BGR2GRAY);
string face_cascade_name="haarcascade_frontalface_alt.xml";
CascadeClassifier face_cascade;
face_cascade.load(face_cascade_name);

face_cascade.detectMultiScale(ImgGray,faces,1.1,2,0|CV_HAAR_SCALE_IMAGE);

Answer 1

The file "haarcascade_frontalface_alt.xml" was missing. I copied it from OpenCV data folder and it works now.