Video Analysis
==============
.. highlight:: cpp
gpu::BroxOpticalFlow
--------------------
.. ocv:class:: 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::GoodFeaturesToTrackDetector_GPU
------------------------------------
.. ocv:class:: gpu::GoodFeaturesToTrackDetector_GPU
Class used for strong corners detection on an image. ::
class GoodFeaturesToTrackDetector_GPU
{
public:
explicit GoodFeaturesToTrackDetector_GPU(int maxCorners_ = 1000, double qualityLevel_ = 0.01, double minDistance_ = 0.0,
int blockSize_ = 3, bool useHarrisDetector_ = false, double harrisK_ = 0.04);
void operator ()(const GpuMat& image, GpuMat& corners, const GpuMat& mask = GpuMat());
int maxCorners;
double qualityLevel;
double minDistance;
int blockSize;
bool useHarrisDetector;
double harrisK;
void releaseMemory();
};
The class finds the most prominent corners in the image.
.. seealso:: :ocv:func:`goodFeaturesToTrack`
gpu::GoodFeaturesToTrackDetector_GPU::GoodFeaturesToTrackDetector_GPU
---------------------------------------------------------------------
Constructor.
.. ocv:function:: gpu::GoodFeaturesToTrackDetector_GPU::GoodFeaturesToTrackDetector_GPU(int maxCorners = 1000, double qualityLevel = 0.01, double minDistance = 0.0, int blockSize = 3, bool useHarrisDetector = false, double harrisK = 0.04)
:param maxCorners: Maximum number of corners to return. If there are more corners than are found, the strongest of them is returned.
:param qualityLevel: Parameter characterizing the minimal accepted quality of image corners. The parameter value is multiplied by the best corner quality measure, which is the minimal eigenvalue (see :ocv:func:`gpu::cornerMinEigenVal` ) or the Harris function response (see :ocv:func:`gpu::cornerHarris` ). The corners with the quality measure less than the product are rejected. For example, if the best corner has the quality measure = 1500, and the ``qualityLevel=0.01`` , then all the corners with the quality measure less than 15 are rejected.
:param minDistance: Minimum possible Euclidean distance between the returned corners.
:param blockSize: Size of an average block for computing a derivative covariation matrix over each pixel neighborhood. See :ocv:func:`cornerEigenValsAndVecs` .
:param useHarrisDetector: Parameter indicating whether to use a Harris detector (see :ocv:func:`gpu::cornerHarris`) or :ocv:func:`gpu::cornerMinEigenVal`.
:param harrisK: Free parameter of the Harris detector.
gpu::GoodFeaturesToTrackDetector_GPU::operator ()
-------------------------------------------------
Finds the most prominent corners in the image.
.. ocv:function:: void gpu::GoodFeaturesToTrackDetector_GPU::operator ()(const GpuMat& image, GpuMat& corners, const GpuMat& mask = GpuMat())
:param image: Input 8-bit, single-channel image.
:param corners: Output vector of detected corners (it will be one row matrix with CV_32FC2 type).
:param mask: Optional region of interest. If the image is not empty (it needs to have the type ``CV_8UC1`` and the same size as ``image`` ), it specifies the region in which the corners are detected.
.. seealso:: :ocv:func:`goodFeaturesToTrack`
gpu::GoodFeaturesToTrackDetector_GPU::releaseMemory
---------------------------------------------------
Releases inner buffers memory.
.. ocv:function:: void gpu::GoodFeaturesToTrackDetector_GPU::releaseMemory()
gpu::FarnebackOpticalFlow
-------------------------
.. ocv:class:: 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.
.. ocv:function:: void gpu::FarnebackOpticalFlow::operator ()(const GpuMat &frame0, const GpuMat &frame1, GpuMat &flowx, GpuMat &flowy, Stream &s = Stream::Null())
:param frame0: First 8-bit gray-scale input image
:param frame1: Second 8-bit gray-scale input image
:param flowx: Flow horizontal component
:param flowy: Flow vertical component
:param s: Stream
.. seealso:: :ocv:func:`calcOpticalFlowFarneback`
gpu::FarnebackOpticalFlow::releaseMemory
----------------------------------------
Releases unused auxiliary memory buffers.
.. ocv:function:: void gpu::FarnebackOpticalFlow::releaseMemory()
gpu::PyrLKOpticalFlow
---------------------
.. ocv:class:: 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;
double derivLambda;
bool useInitialFlow;
float minEigThreshold;
bool getMinEigenVals;
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.
.. seealso:: :ocv:func:`calcOpticalFlowPyrLK`
gpu::PyrLKOpticalFlow::sparse
-----------------------------
Calculate an optical flow for a sparse feature set.
.. ocv:function:: void gpu::PyrLKOpticalFlow::sparse(const GpuMat& prevImg, const GpuMat& nextImg, const GpuMat& prevPts, GpuMat& nextPts, GpuMat& status, GpuMat* err = 0)
:param prevImg: First 8-bit input image (supports both grayscale and color images).
:param nextImg: Second input image of the same size and the same type as ``prevImg`` .
:param prevPts: Vector of 2D points for which the flow needs to be found. It must be one row matrix with CV_32FC2 type.
:param nextPts: Output vector of 2D points (with single-precision floating-point coordinates) containing the calculated new positions of input features in the second image. When ``useInitialFlow`` is true, the vector must have the same size as in the input.
:param status: Output status vector (CV_8UC1 type). Each element of the vector is set to 1 if the flow for the corresponding features has been found. Otherwise, it is set to 0.
:param err: Output vector (CV_32FC1 type) that contains the difference between patches around the original and moved points or min eigen value if ``getMinEigenVals`` is checked. It can be NULL, if not needed.
.. seealso:: :ocv:func:`calcOpticalFlowPyrLK`
gpu::PyrLKOpticalFlow::dense
-----------------------------
Calculate dense optical flow.
.. ocv:function:: void gpu::PyrLKOpticalFlow::dense(const GpuMat& prevImg, const GpuMat& nextImg, GpuMat& u, GpuMat& v, GpuMat* err = 0)
:param prevImg: First 8-bit grayscale input image.
:param nextImg: Second input image of the same size and the same type as ``prevImg`` .
:param u: Horizontal component of the optical flow of the same size as input images, 32-bit floating-point, single-channel
:param v: Vertical component of the optical flow of the same size as input images, 32-bit floating-point, single-channel
:param err: Output vector (CV_32FC1 type) that contains the difference between patches around the original and moved points or min eigen value if ``getMinEigenVals`` is checked. It can be NULL, if not needed.
gpu::PyrLKOpticalFlow::releaseMemory
------------------------------------
Releases inner buffers memory.
.. ocv:function:: void gpu::PyrLKOpticalFlow::releaseMemory()
gpu::interpolateFrames
----------------------
Interpolate frames (images) using provided optical flow (displacement field).
.. ocv:function:: void gpu::interpolateFrames(const GpuMat& frame0, const GpuMat& frame1, const GpuMat& fu, const GpuMat& fv, const GpuMat& bu, const GpuMat& bv, float pos, GpuMat& newFrame, GpuMat& buf, Stream& stream = Stream::Null())
:param frame0: First frame (32-bit floating point images, single channel).
:param frame1: Second frame. Must have the same type and size as ``frame0`` .
:param fu: Forward horizontal displacement.
:param fv: Forward vertical displacement.
:param bu: Backward horizontal displacement.
:param bv: Backward vertical displacement.
:param pos: New frame position.
:param newFrame: Output image.
:param buf: Temporary buffer, will have width x 6*height size, CV_32FC1 type and contain 6 GpuMat: occlusion masks for first frame, occlusion masks for second, interpolated forward horizontal flow, interpolated forward vertical flow, interpolated backward horizontal flow, interpolated backward vertical flow.
:param stream: Stream for the asynchronous version.
.. [Brox2004] T. Brox, A. Bruhn, N. Papenberg, J. Weickert. *High accuracy optical flow estimation based on a theory for warping*. ECCV 2004.