Skin Color Detection on ROI Image on Android

edit

Hi There, I Need your help to get solution. I have a source code that can detect right hand using Android. I work it with original source from android sample "face detector". with simple work, i can change that face detector to become right hand detector. this is android source to detect desired object :

 @Override
protected Bitmap processFrame(VideoCapture capture) {
    capture.retrieve(mRgba, Highgui.CV_CAP_ANDROID_COLOR_FRAME_RGBA);
    capture.retrieve(mGray, Highgui.CV_CAP_ANDROID_GREY_FRAME);

    if (mCascade != null) {
        int height = mGray.rows();
        int handSize = Math.round(height * Isign.minHandSize);
        List<Rect> hand = new LinkedList<Rect>();
        mCascade.detectMultiScale(mGray, hand, 1.1, 2, 2 // TODO: objdetect.CV_HAAR_SCALE_IMAGE
                ,new Size(handSize, handSize));           
        for (Rect r : hand)
            Core.rectangle(mRgba, r.tl(), r.br(), new Scalar(255, 255, 255, 255), 3);
    }
    Bitmap bmp = Bitmap.createBitmap(mRgba.cols(), mRgba.rows(), Bitmap.Config.ARGB_8888);
    if (Utils.matToBitmap(mRgba, bmp))
        return bmp;
    bmp.recycle();
    return null;
}

So with this code :

for (Rect r : hand)
                Core.rectangle(mRgba, r.tl(), r.br(), new Scalar(255, 255, 255, 255), 3);

I can get ROI Image at every frame from video capture.

My Problem is :

How can i process that ROI Images (actually frame on the rect area) to real time skin detection and preview in android screen realtime also. so, maybe this image can descibe clearly what i want to do : (second picture edited by photoshop)

This Original Hand Detect

This My Edited Picture from PS : I want this

Thank you So Much for Your Answer... :)