BackgroundSubtractorMOG2

Objective-C

@interface BackgroundSubtractorMOG2 : BackgroundSubtractor

Swift

class BackgroundSubtractorMOG2 : BackgroundSubtractor

Gaussian Mixture-based Background/Foreground Segmentation Algorithm.

The class implements the Gaussian mixture model background subtraction described in CITE: Zivkovic2004 and CITE: Zivkovic2006 .

Member of Video

Methods

  • Returns the shadow detection flag

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

    Declaration

    Objective-C

    - (BOOL)getDetectShadows;

    Swift

    func getDetectShadows() -> Bool

  • 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.

    Declaration

    Objective-C

    - (double)getBackgroundRatio;

    Swift

    func getBackgroundRatio() -> Double

  • 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.

    Declaration

    Objective-C

    - (double)getComplexityReductionThreshold;

    Swift

    func getComplexityReductionThreshold() -> Double

  • 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.

    Declaration

    Objective-C

    - (double)getShadowThreshold;

    Swift

    func getShadowThreshold() -> Double

  • Returns the initial variance of each gaussian component

    Declaration

    Objective-C

    - (double)getVarInit;

    Swift

    func getVarInit() -> Double

  • Declaration

    Objective-C

    - (double)getVarMax NS_SWIFT_NAME(getVarMax());

    Swift

    func getVarMax() -> Double

  • Declaration

    Objective-C

    - (double)getVarMin NS_SWIFT_NAME(getVarMin());

    Swift

    func getVarMin() -> Double

  • 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.

    Declaration

    Objective-C

    - (double)getVarThreshold;

    Swift

    func getVarThreshold() -> Double

  • 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.

    Declaration

    Objective-C

    - (double)getVarThresholdGen;

    Swift

    func getVarThresholdGen() -> Double

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

    Declaration

    Objective-C

    - (int)getHistory;

    Swift

    func getHistory() -> Int32

  • Returns the number of gaussian components in the background model

    Declaration

    Objective-C

    - (int)getNMixtures;

    Swift

    func getNMixtures() -> Int32

  • 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.

    Declaration

    Objective-C

    - (int)getShadowValue;

    Swift

    func getShadowValue() -> Int32

  • Computes a foreground mask.

    Declaration

    Objective-C

    - (void)apply:(nonnull Mat *)image
          fgmask:(nonnull Mat *)fgmask
    learningRate:(double)learningRate;

    Swift

    func apply(image: Mat, fgmask: Mat, learningRate: Double)

    Parameters

    image

    Next video frame. Floating point frame will be used without scaling and should be in range

    [0,255]
    .
    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.

  • Computes a foreground mask.

    Declaration

    Objective-C

    - (void)apply:(nonnull Mat *)image fgmask:(nonnull Mat *)fgmask;

    Swift

    func apply(image: Mat, fgmask: Mat)

    Parameters

    image

    Next video frame. Floating point frame will be used without scaling and should be in range

    [0,255]
    .
    fgmask

    The output foreground mask as an 8-bit binary image. 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.

  • Sets the “background ratio” parameter of the algorithm

    Declaration

    Objective-C

    - (void)setBackgroundRatio:(double)ratio;

    Swift

    func setBackgroundRatio(ratio: Double)

  • Sets the complexity reduction threshold

    Declaration

    Objective-C

    - (void)setComplexityReductionThreshold:(double)ct;

    Swift

    func setComplexityReductionThreshold(ct: Double)

  • Enables or disables shadow detection

    Declaration

    Objective-C

    - (void)setDetectShadows:(BOOL)detectShadows;

    Swift

    func setDetectShadows(detectShadows: Bool)

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

    Declaration

    Objective-C

    - (void)setHistory:(int)history;

    Swift

    func setHistory(history: Int32)

  • Sets the number of gaussian components in the background model.

     The model needs to be reinitalized to reserve memory.

    Declaration

    Objective-C

    - (void)setNMixtures:(int)nmixtures;

    Swift

    func setNMixtures(nmixtures: Int32)

  • Sets the shadow threshold

    Declaration

    Objective-C

    - (void)setShadowThreshold:(double)threshold;

    Swift

    func setShadowThreshold(threshold: Double)

  • Sets the shadow value

    Declaration

    Objective-C

    - (void)setShadowValue:(int)value;

    Swift

    func setShadowValue(value: Int32)

  • Sets the initial variance of each gaussian component

    Declaration

    Objective-C

    - (void)setVarInit:(double)varInit;

    Swift

    func setVarInit(varInit: Double)

  • Declaration

    Objective-C

    - (void)setVarMax:(double)varMax NS_SWIFT_NAME(setVarMax(varMax:));

    Swift

    func setVarMax(varMax: Double)

  • Declaration

    Objective-C

    - (void)setVarMin:(double)varMin NS_SWIFT_NAME(setVarMin(varMin:));

    Swift

    func setVarMin(varMin: Double)

  • Sets the variance threshold for the pixel-model match

    Declaration

    Objective-C

    - (void)setVarThreshold:(double)varThreshold;

    Swift

    func setVarThreshold(varThreshold: Double)

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

    Declaration

    Objective-C

    - (void)setVarThresholdGen:(double)varThresholdGen;

    Swift

    func setVarThresholdGen(varThresholdGen: Double)