运动跟踪（七）：BackgroundSubtractorMOG2（），背景差

class CV_EXPORTS_W BackgroundSubtractorMOG2 : public BackgroundSubtractor
{
public:
    //! the default constructor
    CV_WRAP BackgroundSubtractorMOG2();
    //! the full constructor that takes the length of the history, the number of gaussian mixtures, the background ratio parameter and the noise strength
    CV_WRAP BackgroundSubtractorMOG2(int history,  float varThreshold, bool bShadowDetection=true);
    //! the destructor
    virtual ~BackgroundSubtractorMOG2();
    //! the update operator
    virtual void operator()(InputArray image, OutputArray fgmask, double learningRate=-1);

    //! computes a background image which are the mean of all background gaussians
    virtual void getBackgroundImage(OutputArray backgroundImage) const;

    //! re-initiaization method
    virtual void initialize(Size frameSize, int frameType);

    virtual AlgorithmInfo* info() const;

protected:
    Size frameSize;
    int frameType;
    Mat bgmodel;
    Mat bgmodelU