OpenCV Cascade Classifier load error iOS

Question

Currently I am trying to using an OpenCV Cascade Classifier to detect faces in my iOS app. The problem is that when I go to load the classifier, it fails because the pathname to the "haarcascade_frontalface_alt.xml" isn't correct.

Here is my code:

cv::String face_cascade_name = "haarcascade_frontalface_alt.xml";

void detectFaces(cv::Mat frame){

cv::CascadeClassifier face_cascade;
if (face_cascade.load(face_cascade_name)){
    printf("Load complete");
}else{
    printf("Load error");
}
std::vector<cv::Rect> faces;

std::vector<cv::Mat> rgbChannels(3);
cv::split(frame, rgbChannels); // Making the frame gray scale
cv::Mat frame_gray = rgbChannels[2];

face_cascade.detectMultiScale(frame_gray, faces, 1.1, 2, 0|CV_HAAR_SCALE_IMAGE|CV_HAAR_FIND_BIGGEST_OBJECT, cv::Size(150,150));

if(faces.size()> 0){
    printf("TRUE");
}

}

Since this is an iOS project I don't know how to find the path of the required xml file in the framework. What is the proper way to load a Cascade Classifier into an iOS project? Or, what is the correct way to include the right filename so that it sees it properly?

Any help would be appreciated.

Answer 1

In iOS, you need to locate the file path within the app bunnle. Something like this:

// get main app bundle
NSBundle * appBundle = [NSBundle mainBundle];

// constant file name
NSString * cascadeName = @"haarcascade_frontalface_alt";
NSString * cascadeType = @"xml";

// get file path in bundle
NSString * cascadePathInBundle = [appBundle pathForResource: cascadeName ofType: cascadeType];

// convert NSString to std::string
std::string cascadePath([cascadePathInBundle UTF8String]);

// load cascade
if (face_cascade.load(cascadePath)){
    printf("Load complete");
}else{
    printf("Load error");
}