hand detection - with rotated hand about js-objectdetect

[mtschirs]

A standard technique is to rotate the image e.g. in 45° steps before applying the detector.

If you only care about the 90° rotations, you could apply these rotations to the classifier instead. That functionality is not implemented in js-objectdetect but could be an interestind addition. The implementation would follow the pattern of the mirrorClassifier method which works pretty similar.

In the end, however, you can't avoid to either always rotate the image in every step and re-run the classification on the rotated images OR rotate the classifier in a preliminary step and re-run the classification with the rotated classifiers.

Edit: If you want to detect the hand as shown in your second picture with the palms facing away from the camera however, you would need to train another classifier. With a single classifier, you can only detect rotations of the object said classifier was trained on if the plane of rotation is facing (perpendicular to) the camera (i.e. the palms are always facing the camera).

[jonatas]

Thank you @mtschirs! I'll try look how the mirrorClassifier works and implement the rotation...

How can I see the images used on the current classifiers?

Thank you for tell me about the classifiers. I'll try to switch to a fist hand and keep using the current classifiers only rotated...

How much complex is feed a new classifier on js-objectdetect? I need to crop the images on the limits what I want to trainee? There's a script to automate these?

[mtschirs]

Unfortunately the js-objectdetect library is not very well documented right now. However, there are a lot of sources online about the classifiers used. Keywords would be "Haar Cascade Classifiers". To quickly grasp the concept of how the classifier works, have a look at http://docs.opencv.org/master/d7/d8b/tutorial_py_face_detection.html#gsc.tab=0

If you want to train your own classifier this might provide a good starting point: http://docs.opencv.org/2.4/doc/user_guide/ug_traincascade.html

If you want to know more about the specific classifiers provided with js-objectdetect, look into the classifier license file and follow the references. I am sure you will find papers on most of them detailing the training process.

[jonatas]

Thank you for the resources @mtschirs! I'll 👀!