Optical Flow

gpu::BroxOpticalFlow

Class computing the optical flow for two images using Brox et al Optical Flow algorithm ([Brox2004]).

class BroxOpticalFlow
{
public:
    BroxOpticalFlow(float alpha_, float gamma_, float scale_factor_, int inner_iterations_, int outer_iterations_, int solver_iterations_);

    //! Compute optical flow
    //! frame0 - source frame (supports only CV_32FC1 type)
    //! frame1 - frame to track (with the same size and type as frame0)
    //! u      - flow horizontal component (along x axis)
    //! v      - flow vertical component (along y axis)
    void operator ()(const GpuMat& frame0, const GpuMat& frame1, GpuMat& u, GpuMat& v, Stream& stream = Stream::Null());

    //! flow smoothness
    float alpha;

    //! gradient constancy importance
    float gamma;

    //! pyramid scale factor
    float scale_factor;

    //! number of lagged non-linearity iterations (inner loop)
    int inner_iterations;

    //! number of warping iterations (number of pyramid levels)
    int outer_iterations;

    //! number of linear system solver iterations
    int solver_iterations;

    GpuMat buf;
};

gpu::FarnebackOpticalFlow

Class computing a dense optical flow using the Gunnar Farneback’s algorithm.

class CV_EXPORTS FarnebackOpticalFlow
{
public:
    FarnebackOpticalFlow()
    {
        numLevels = 5;
        pyrScale = 0.5;
        fastPyramids = false;
        winSize = 13;
        numIters = 10;
        polyN = 5;
        polySigma = 1.1;
        flags = 0;
    }

    int numLevels;
    double pyrScale;
    bool fastPyramids;
    int winSize;
    int numIters;
    int polyN;
    double polySigma;
    int flags;

    void operator ()(const GpuMat &frame0, const GpuMat &frame1, GpuMat &flowx, GpuMat &flowy, Stream &s = Stream::Null());

    void releaseMemory();

private:
    /* hidden */
};

gpu::FarnebackOpticalFlow::operator ()

Computes a dense optical flow using the Gunnar Farneback’s algorithm.

gpu::FarnebackOpticalFlow::releaseMemory

Releases unused auxiliary memory buffers.

gpu::PyrLKOpticalFlow

Class used for calculating an optical flow.

class PyrLKOpticalFlow
{
public:
    PyrLKOpticalFlow();

    void sparse(const GpuMat& prevImg, const GpuMat& nextImg, const GpuMat& prevPts, GpuMat& nextPts,
        GpuMat& status, GpuMat* err = 0);

    void dense(const GpuMat& prevImg, const GpuMat& nextImg, GpuMat& u, GpuMat& v, GpuMat* err = 0);

    Size winSize;
    int maxLevel;
    int iters;
    bool useInitialFlow;

    void releaseMemory();
};

The class can calculate an optical flow for a sparse feature set or dense optical flow using the iterative Lucas-Kanade method with pyramids.

gpu::PyrLKOpticalFlow::sparse

Calculate an optical flow for a sparse feature set.

gpu::PyrLKOpticalFlow::dense

Calculate dense optical flow.

gpu::PyrLKOpticalFlow::releaseMemory

Releases inner buffers memory.

gpu::interpolateFrames

Interpolates frames (images) using provided optical flow (displacement field).

[Brox2004]

Brox, A. Bruhn, N. Papenberg, J. Weickert. High accuracy optical flow estimation based on a theory for warping. ECCV 2004.