cv::BackgroundSubtractorMOG2 Class Reference

Gaussian Mixture-based Background/Foreground Segmentation Algorithm. More...

#include <background_segm.hpp>

Inheritance diagram for cv::BackgroundSubtractorMOG2:

Public Member Functions
virtual CV_WRAP int	getHistory () const =0
	Returns the number of last frames that affect the background model.
virtual CV_WRAP void	setHistory (int history)=0
	Sets the number of last frames that affect the background model.
virtual CV_WRAP int	getNMixtures () const =0
	Returns the number of gaussian components in the background model.
virtual CV_WRAP void	setNMixtures (int nmixtures)=0
	Sets the number of gaussian components in the background model.
virtual CV_WRAP double	getBackgroundRatio () const =0
	Returns the "background ratio" parameter of the algorithm.
virtual CV_WRAP void	setBackgroundRatio (double ratio)=0
	Sets the "background ratio" parameter of the algorithm.
virtual CV_WRAP double	getVarThreshold () const =0
	Returns the variance threshold for the pixel-model match.
virtual CV_WRAP void	setVarThreshold (double varThreshold)=0
	Sets the variance threshold for the pixel-model match.
virtual CV_WRAP double	getVarThresholdGen () const =0
	Returns the variance threshold for the pixel-model match used for new mixture component generation.
virtual CV_WRAP void	setVarThresholdGen (double varThresholdGen)=0
	Sets the variance threshold for the pixel-model match used for new mixture component generation.
virtual CV_WRAP double	getVarInit () const =0
	Returns the initial variance of each gaussian component.
virtual CV_WRAP void	setVarInit (double varInit)=0
	Sets the initial variance of each gaussian component.
virtual CV_WRAP double	getVarMin () const =0
virtual CV_WRAP void	setVarMin (double varMin)=0
virtual CV_WRAP double	getVarMax () const =0
virtual CV_WRAP void	setVarMax (double varMax)=0
virtual CV_WRAP double	getComplexityReductionThreshold () const =0
	Returns the complexity reduction threshold.
virtual CV_WRAP void	setComplexityReductionThreshold (double ct)=0
	Sets the complexity reduction threshold.
virtual CV_WRAP bool	getDetectShadows () const =0
	Returns the shadow detection flag.
virtual CV_WRAP void	setDetectShadows (bool detectShadows)=0
	Enables or disables shadow detection.
virtual CV_WRAP int	getShadowValue () const =0
	Returns the shadow value.
virtual CV_WRAP void	setShadowValue (int value)=0
	Sets the shadow value.
virtual CV_WRAP double	getShadowThreshold () const =0
	Returns the shadow threshold.
virtual CV_WRAP void	setShadowThreshold (double threshold)=0
	Sets the shadow threshold.
virtual CV_WRAP void	apply (InputArray image, OutputArray fgmask, double learningRate=-1) CV_OVERRIDE=0
	Computes a foreground mask.
Public Member Functions inherited from cv::BackgroundSubtractor
virtual CV_WRAP void	getBackgroundImage (OutputArray backgroundImage) const =0
	Computes a background image.
Public Member Functions inherited from cv::Algorithm
	Algorithm ()
virtual	~Algorithm ()
virtual CV_WRAP void	clear ()
	Clears the algorithm state.
virtual CV_WRAP void	write (FileStorage &fs) const
	Stores algorithm parameters in a file storage.
CV_WRAP void	write (FileStorage &fs, const String &name) const
void	write (const Ptr< FileStorage > &fs, const String &name=String()) const
virtual CV_WRAP void	read (const FileNode &fn)
	Reads algorithm parameters from a file storage.
virtual CV_WRAP bool	empty () const
	Returns true if the Algorithm is empty (e.g. in the very beginning or after unsuccessful read.
virtual CV_WRAP void	save (const String &filename) const
virtual CV_WRAP String	getDefaultName () const

Additional Inherited Members
Static Public Member Functions inherited from cv::Algorithm
template<typename _Tp >
static Ptr< _Tp >	read (const FileNode &fn)
	Reads algorithm from the file node.
template<typename _Tp >
static Ptr< _Tp >	load (const String &filename, const String &objname=String())
	Loads algorithm from the file.
template<typename _Tp >
static Ptr< _Tp >	loadFromString (const String &strModel, const String &objname=String())
	Loads algorithm from a String.
Protected Member Functions inherited from cv::Algorithm
void	writeFormat (FileStorage &fs) const

Detailed Description

Gaussian Mixture-based Background/Foreground Segmentation Algorithm.

The class implements the Gaussian mixture model background subtraction described in [Zivkovic2004] and [Zivkovic2006] .

Member Function Documentation

apply()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::apply ( InputArray  image, OutputArray  fgmask, double  learningRate = -1  )

pure virtual

Computes a foreground mask.

Parameters

image	Next video frame. Floating point frame will be used without scaling and should be in range .
fgmask	The output foreground mask as an 8-bit binary image.
learningRate	The value between 0 and 1 that indicates how fast the background model is learnt. Negative parameter value makes the algorithm to use some automatically chosen learning rate. 0 means that the background model is not updated at all, 1 means that the background model is completely reinitialized from the last frame.

Implements cv::BackgroundSubtractor.

getBackgroundRatio()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getBackgroundRatio ( ) const

pure virtual

Returns the "background ratio" parameter of the algorithm.

If a foreground pixel keeps semi-constant value for about backgroundRatio*history frames, it's considered background and added to the model as a center of a new component. It corresponds to TB parameter in the paper.

getComplexityReductionThreshold()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getComplexityReductionThreshold ( ) const

pure virtual

Returns the complexity reduction threshold.

This parameter defines the number of samples needed to accept to prove the component exists. CT=0.05 is a default value for all the samples. By setting CT=0 you get an algorithm very similar to the standard Stauffer&Grimson algorithm.

getDetectShadows()

virtual CV_WRAP bool cv::BackgroundSubtractorMOG2::getDetectShadows ( ) const

pure virtual

Returns the shadow detection flag.

If true, the algorithm detects shadows and marks them. See createBackgroundSubtractorMOG2 for details.

getHistory()

virtual CV_WRAP int cv::BackgroundSubtractorMOG2::getHistory ( ) const

pure virtual

Returns the number of last frames that affect the background model.

getNMixtures()

virtual CV_WRAP int cv::BackgroundSubtractorMOG2::getNMixtures ( ) const

pure virtual

Returns the number of gaussian components in the background model.

getShadowThreshold()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getShadowThreshold ( ) const

pure virtual

Returns the shadow threshold.

A shadow is detected if pixel is a darker version of the background. The shadow threshold (Tau in the paper) is a threshold defining how much darker the shadow can be. Tau= 0.5 means that if a pixel is more than twice darker then it is not shadow. See Prati, Mikic, Trivedi and Cucchiara, Detecting Moving Shadows...*, IEEE PAMI,2003.

getShadowValue()

virtual CV_WRAP int cv::BackgroundSubtractorMOG2::getShadowValue ( ) const

pure virtual

Returns the shadow value.

Shadow value is the value used to mark shadows in the foreground mask. Default value is 127. Value 0 in the mask always means background, 255 means foreground.

getVarInit()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getVarInit ( ) const

pure virtual

Returns the initial variance of each gaussian component.

getVarMax()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getVarMax ( ) const

pure virtual

getVarMin()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getVarMin ( ) const

pure virtual

getVarThreshold()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getVarThreshold ( ) const

pure virtual

Returns the variance threshold for the pixel-model match.

The main threshold on the squared Mahalanobis distance to decide if the sample is well described by the background model or not. Related to Cthr from the paper.

getVarThresholdGen()

virtual CV_WRAP double cv::BackgroundSubtractorMOG2::getVarThresholdGen ( ) const

pure virtual

Returns the variance threshold for the pixel-model match used for new mixture component generation.

Threshold for the squared Mahalanobis distance that helps decide when a sample is close to the existing components (corresponds to Tg in the paper). If a pixel is not close to any component, it is considered foreground or added as a new component. 3 sigma => Tg=3*3=9 is default. A smaller Tg value generates more components. A higher Tg value may result in a small number of components but they can grow too large.

setBackgroundRatio()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setBackgroundRatio ( double  ratio )

pure virtual

Sets the "background ratio" parameter of the algorithm.

setComplexityReductionThreshold()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setComplexityReductionThreshold ( double  ct )

pure virtual

Sets the complexity reduction threshold.

setDetectShadows()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setDetectShadows ( bool  detectShadows )

pure virtual

Enables or disables shadow detection.

setHistory()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setHistory ( int  history )

pure virtual

Sets the number of last frames that affect the background model.

setNMixtures()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setNMixtures ( int  nmixtures )

pure virtual

Sets the number of gaussian components in the background model.

The model needs to be reinitalized to reserve memory.

setShadowThreshold()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setShadowThreshold ( double  threshold )

pure virtual

Sets the shadow threshold.

setShadowValue()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setShadowValue ( int  value )

pure virtual

Sets the shadow value.

setVarInit()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setVarInit ( double  varInit )

pure virtual

Sets the initial variance of each gaussian component.

setVarMax()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setVarMax ( double  varMax )

pure virtual

setVarMin()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setVarMin ( double  varMin )

pure virtual

setVarThreshold()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setVarThreshold ( double  varThreshold )

pure virtual

Sets the variance threshold for the pixel-model match.

setVarThresholdGen()

virtual CV_WRAP void cv::BackgroundSubtractorMOG2::setVarThresholdGen ( double  varThresholdGen )

pure virtual

Sets the variance threshold for the pixel-model match used for new mixture component generation.

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The documentation for this class was generated from the following file:

• build/release/_deps/opencv-src/include/opencv4/opencv2/video/background_segm.hpp