How to start to program face recognition?

edit

the haarcascades are used for face detection, the eigen/fisher/lbp methods for face recognition

but a typical program will need both, a haar-detection first, to restrict the processing to the face area, and a face-recognizer after that.

let's think for now, that you got pre-cropped images of the persons (say, 90x90).

you create a facerecogizer:

Ptr<FaceRecognizer> model = createEigenFaceRecognizer();

then it needs to get trained. for every person you need some images(say 10), load them (grayscale), and put them into a vector<mat>. also you need to track which person it was, so it needs another vector<int> with person-ids, one for each image. now we can train it:

model->train(images, labels);

after that is done, you can test if it regognizes persons, you give it a grayscale image ( same size ) and call:

int predictedLabel = model->predict(testSample);

you'll get back the id of the person it was most similar to.

again, look here for the recognition example, and here for the detection