Tracking of detected faces using OpenCV on iOS [closed]

asked 2013-03-13 12:54:16 -0600

First, a quick bit of background: I am fairly new to iOS and am attempting to detect faces using OpenCV on an iOS device. I was able to get the iOS openCV sample code working fine using the sample code here:

This results in a useful method that is called for each frame polled from the camera:

- (void)processImage:(Mat&)image;
    // Do some OpenCV stuff with the image
    Mat image_copy;
    cvtColor(image, image_copy, CV_BGRA2BGR);

    // invert image
    bitwise_not(image_copy, image_copy);
    cvtColor(image_copy, image, CV_BGR2BGRA);

In this example, it successfully inverted the frame from the camera and displays on the device. This is useful, as I can subsitute my won OpenCV C++ code into here for whatever image processing I want to do with the frame.

Now, I wish to get face tracking implemented. There are header files for a detection based tracker in OpenCV 2.4.2 onwards called “opencv2/contrib/detection_based_tracker.hpp”. It defines a class called DetectionBasedTracker. The tracking mechanism it defines uses haar cascades in the background to detect objects. The reason that I wish to use this temporal tracking method rather than frame by frame face detection is that the tracking is much faster than the OpenCV Haar implementation. A guide on how to implement it is demonstrated here:

I had success in implementing this code in C++ on an Android device. The main code is as follows:

DetectionBasedTracker::Parameters param;
param.maxObjectSize = 400;
param.maxTrackLifetime = 20;
param.minDetectionPeriod = 7;
param.minNeighbors = 3;
param.minObjectSize = 20;
param.scaleFactor = 1.1;

// The object needs to be defined using the constructor with the above 
// declared parameter structure. Then the method is called 
// to initialize the tracking.
DetectionBasedTracker obj = DetectionBasedTracker("haarcascade_frontalface_alt.xml",param);;

And so, for each frame, I can process it to detect the bounding boxes of faces using the lines:

vector< Rect_<int> > faces;

Now, the issue. In Objective C, how to I create the "DetectionBasedTracker obj" object so that it can be used in the - (void)processImage:(Mat&)image; method? I do not know what calls the processImage method so I do not now if I can pass it that way. Is there a way to make the "DetectionBasedTracker obj" global? and if so, how would I do that, and is this the correct way of doing it?

Thanks for your help!

edit retag flag offensive reopen merge delete

Closed for the following reason question is not relevant or outdated by sturkmen
close date 2020-10-20 11:14:05.577810


Hi, did you figure out a way to do it? Any help would be appreciated, thanks!

gunshi gravatar imagegunshi ( 2016-01-11 02:09:51 -0600 )edit