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added background/foreground segmentation algorithm with shadow detection (by Zoran Zivkovic)

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// this list of conditions and the following disclaimer.
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/*//Implementation of the Gaussian mixture model background subtraction from:
//
//"Improved adaptive Gausian mixture model for background subtraction"
//Z.Zivkovic
//International Conference Pattern Recognition, UK, August, 2004
//http://www.zoranz.net/Publications/zivkovic2004ICPR.pdf
//The code is very fast and performs also shadow detection.
//Number of Gausssian components is adapted per pixel.
//
// and
//
//"Efficient Adaptive Density Estimapion per Image Pixel for the Task of Background Subtraction"
//Z.Zivkovic, F. van der Heijden
//Pattern Recognition Letters, vol. 27, no. 7, pages 773-780, 2006.
//
//The algorithm similar to the standard Stauffer&Grimson algorithm with
//additional selection of the number of the Gaussian components based on:
//
//"Recursive unsupervised learning of finite mixture models "
//Z.Zivkovic, F.van der Heijden
//IEEE Trans. on Pattern Analysis and Machine Intelligence, vol.26, no.5, pages 651-656, 2004
//http://www.zoranz.net/Publications/zivkovic2004PAMI.pdf
//
//
//
//Example usage as part of the CvBGStatModel:
// CvBGStatModel* bg_model = cvCreateGaussianBGModel2( first_frame );
//
// //update for each frame
// cvUpdateBGStatModel( tmp_frame, bg_model );//segmentation result is in bg_model->foreground
//
// //release at the program termination
// cvReleaseBGStatModel( &bg_model );
//
//Author: Z.Zivkovic, www.zoranz.net
//Date: 27-April-2005, Version:0.9
///////////*/
#include "cvaux.h"
#include "cvaux_mog2.h"
int _icvRemoveShadowGMM(long posPixel,
float red, float green, float blue,
unsigned char nModes,
CvPBGMMGaussian* m_aGaussians,
float m_fTb,
float m_fTB,
float m_fTau)
{
//calculate distances to the modes (+ sort???)
//here we need to go in descending order!!!
long pos;
float tWeight = 0;
float numerator, denominator;
// check all the distributions, marked as background:
for (int iModes=0;iModes<nModes;iModes++)
{
pos=posPixel+iModes;
float var = m_aGaussians[pos].sigma;
float muR = m_aGaussians[pos].muR;
float muG = m_aGaussians[pos].muG;
float muB = m_aGaussians[pos].muB;
float weight = m_aGaussians[pos].weight;
tWeight += weight;
numerator = red * muR + green * muG + blue * muB;
denominator = muR * muR + muG * muG + muB * muB;
// no division by zero allowed
if (denominator == 0)
{
break;
};
float a = numerator / denominator;
// if tau < a < 1 then also check the color distortion
if ((a <= 1) && (a >= m_fTau))//m_nBeta=1
{
float dR=a * muR - red;
float dG=a * muG - green;
float dB=a * muB - blue;
//square distance -slower and less accurate
//float maxDistance = cvSqrt(m_fTb*var);
//if ((fabs(dR) <= maxDistance) && (fabs(dG) <= maxDistance) && (fabs(dB) <= maxDistance))
//circle
float dist=(dR*dR+dG*dG+dB*dB);
if (dist<m_fTb*var*a*a)
{
return 2;
}
};
if (tWeight > m_fTB)
{
break;
};
};
return 0;
}
int _icvUpdatePixelBackgroundGMM(long posPixel,
float red, float green, float blue,
unsigned char* pModesUsed,
CvPBGMMGaussian* m_aGaussians,
int m_nM,
float m_fAlphaT,
float m_fTb,
float m_fTB,
float m_fTg,
float m_fSigma,
float m_fPrune)
{
//calculate distances to the modes (+ sort???)
//here we need to go in descending order!!!
long pos;
bool bFitsPDF=0;
bool bBackground=0;
float m_fOneMinAlpha=1-m_fAlphaT;
unsigned char nModes=*pModesUsed;
float totalWeight=0.0f;
//////
//go through all modes
for (int iModes=0;iModes<nModes;iModes++)
{
pos=posPixel+iModes;
float weight = m_aGaussians[pos].weight;
////
//fit not found yet
if (!bFitsPDF)
{
//check if it belongs to some of the modes
//calculate distance
float var = m_aGaussians[pos].sigma;
float muR = m_aGaussians[pos].muR;
float muG = m_aGaussians[pos].muG;
float muB = m_aGaussians[pos].muB;
float dR=muR - red;
float dG=muG - green;
float dB=muB - blue;
///////
//check if it fits the current mode (Factor * sigma)
//square distance -slower and less accurate
//float maxDistance = cvSqrt(m_fTg*var);
//if ((fabs(dR) <= maxDistance) && (fabs(dG) <= maxDistance) && (fabs(dB) <= maxDistance))
//circle
float dist=(dR*dR+dG*dG+dB*dB);
//background? - m_fTb
if ((totalWeight<m_fTB)&&(dist<m_fTb*var))
bBackground=1;
//check fit
if (dist<m_fTg*var)
{
/////
//belongs to the mode
bFitsPDF=1;
//update distribution
float k = m_fAlphaT/weight;
weight=m_fOneMinAlpha*weight+m_fPrune;
weight+=m_fAlphaT;
m_aGaussians[pos].muR = muR - k*(dR);
m_aGaussians[pos].muG = muG - k*(dG);
m_aGaussians[pos].muB = muB - k*(dB);
//limit update speed for cov matrice
//not needed
//k=k>20*m_fAlphaT?20*m_fAlphaT:k;
//float sigmanew = var + k*((0.33*(dR*dR+dG*dG+dB*dB))-var);
//float sigmanew = var + k*((dR*dR+dG*dG+dB*dB)-var);
//float sigmanew = var + k*((0.33*dist)-var);
float sigmanew = var + k*(dist-var);
//limit the variance
//m_aGaussians[pos].sigma = sigmanew>70?70:sigmanew;
//m_aGaussians[pos].sigma = sigmanew>5*m_fSigma?5*m_fSigma:sigmanew;
m_aGaussians[pos].sigma =sigmanew< 4 ? 4 : sigmanew>5*m_fSigma?5*m_fSigma:sigmanew;
//m_aGaussians[pos].sigma =sigmanew< 4 ? 4 : sigmanew>3*m_fSigma?3*m_fSigma:sigmanew;
//m_aGaussians[pos].sigma = m_fSigma;
//sort
//all other weights are at the same place and
//only the matched (iModes) is higher -> just find the new place for it
for (int iLocal = iModes;iLocal>0;iLocal--)
{
long posLocal=posPixel + iLocal;
if (weight < (m_aGaussians[posLocal-1].weight))
{
break;
}
else
{
//swap
CvPBGMMGaussian temp = m_aGaussians[posLocal];
m_aGaussians[posLocal] = m_aGaussians[posLocal-1];
m_aGaussians[posLocal-1] = temp;
}
}
//belongs to the mode
/////
}
else
{
weight=m_fOneMinAlpha*weight+m_fPrune;
//check prune
if (weight<-m_fPrune)
{
weight=0.0;
nModes--;
// bPrune=1;
//break;//the components are sorted so we can skip the rest
}
}
//check if it fits the current mode (2.5 sigma)
///////
}
//fit not found yet
/////
else
{
weight=m_fOneMinAlpha*weight+m_fPrune;
//check prune
if (weight<-m_fPrune)
{
weight=0.0;
nModes--;
}
}
totalWeight+=weight;
m_aGaussians[pos].weight=weight;
}
//go through all modes
//////
//renormalize weights
for (int iLocal = 0; iLocal < nModes; iLocal++)
{
m_aGaussians[posPixel+ iLocal].weight = m_aGaussians[posPixel+ iLocal].weight/totalWeight;
}
//make new mode if needed and exit
if (!bFitsPDF)
{
if (nModes==m_nM)
{
//replace the weakest
}
else
{
//add a new one
nModes++;
}
pos=posPixel+nModes-1;
if (nModes==1)
m_aGaussians[pos].weight=1;
else
m_aGaussians[pos].weight=m_fAlphaT;
//renormalize weights
int iLocal;
for (iLocal = 0; iLocal < nModes-1; iLocal++)
{
m_aGaussians[posPixel+ iLocal].weight *=m_fOneMinAlpha;
}
m_aGaussians[pos].muR=red;
m_aGaussians[pos].muG=green;
m_aGaussians[pos].muB=blue;
m_aGaussians[pos].sigma=m_fSigma;
//sort
//find the new place for it
for (iLocal = nModes-1;iLocal>0;iLocal--)
{
long posLocal=posPixel + iLocal;
if (m_fAlphaT < (m_aGaussians[posLocal-1].weight))
{
break;
}
else
{
//swap
CvPBGMMGaussian temp = m_aGaussians[posLocal];
m_aGaussians[posLocal] = m_aGaussians[posLocal-1];
m_aGaussians[posLocal-1] = temp;
}
}
}
//set the number of modes
*pModesUsed=nModes;
return bBackground;
}
void _icvReplacePixelBackgroundGMM(long pos,
unsigned char* pData,
CvPBGMMGaussian* m_aGaussians)
{
pData[0]=(unsigned char) m_aGaussians[pos].muR;
pData[1]=(unsigned char) m_aGaussians[pos].muG;
pData[2]=(unsigned char) m_aGaussians[pos].muB;
}
void icvUpdatePixelBackgroundGMM(CvGaussBGStatModel2Data* pGMMData,CvGaussBGStatModel2Params* pGMM, float m_fAlphaT, unsigned char* data,unsigned char* output)
{
int size=pGMMData->nSize;
unsigned char* pDataCurrent=data;
unsigned char* pUsedModes=pGMMData->rnUsedModes;
unsigned char* pDataOutput=output;
//some constants
int m_nM=pGMM->nM;
//float m_fAlphaT=pGMM->fAlphaT;
float m_fTb=pGMM->fTb;//Tb - threshold on the Mahalan. dist.
float m_fTB=pGMM->fTB;//1-TF from the paper
float m_fTg=pGMM->fTg;//Tg - when to generate a new component
float m_fSigma=pGMM->fSigma;//initial sigma
float m_fCT=pGMM->fCT;//CT - complexity reduction prior
float m_fPrune=-m_fAlphaT*m_fCT;
float m_fTau=pGMM->fTau;
CvPBGMMGaussian* m_aGaussians=pGMMData->rGMM;
long posPixel=0;
bool m_bShadowDetection=pGMM->bShadowDetection;
unsigned char m_nShadowDetection=pGMM->nShadowDetection;
//go through the image
for (int i=0;i<size;i++)
{
// retrieve the colors
float red = pDataCurrent[0];
float green = pDataCurrent[1];
float blue = pDataCurrent[2];
//update model+ background subtract
int result = _icvUpdatePixelBackgroundGMM(posPixel, red, green, blue,pUsedModes,m_aGaussians,
m_nM,m_fAlphaT, m_fTb, m_fTB, m_fTg, m_fSigma, m_fPrune);
unsigned char nMLocal=*pUsedModes;
if (m_bShadowDetection)
if (!result)
{
result= _icvRemoveShadowGMM(posPixel, red, green, blue,nMLocal,m_aGaussians,
m_fTb,
m_fTB,
m_fTau);
}
switch (result)
{
case 0:
//foreground
(* pDataOutput)=255;
if (pGMM->bRemoveForeground)
{
_icvReplacePixelBackgroundGMM(posPixel,pDataCurrent,m_aGaussians);
}
break;
case 1:
//background
(* pDataOutput)=0;
break;
case 2:
//shadow
(* pDataOutput)=m_nShadowDetection;
if (pGMM->bRemoveForeground)
{
_icvReplacePixelBackgroundGMM(posPixel,pDataCurrent,m_aGaussians);
}
break;
}
posPixel+=m_nM;
pDataCurrent+=3;
pDataOutput++;
pUsedModes++;
}
}
//////////////////////////////////////////////
//implementation as part of the CvBGStatModel
static void CV_CDECL icvReleaseGaussianBGModel2( CvGaussBGModel2** bg_model );
static int CV_CDECL icvUpdateGaussianBGModel2( IplImage* curr_frame, CvGaussBGModel2* bg_model );
CV_IMPL CvBGStatModel*
cvCreateGaussianBGModel2( IplImage* first_frame, CvGaussBGStatModel2Params* parameters )
{
CvGaussBGModel2* bg_model = 0;
int w,h,size;
CV_FUNCNAME( "cvCreateGaussianBGModel2" );
__BEGIN__;
CvGaussBGStatModel2Params params;
if( !CV_IS_IMAGE(first_frame) )
CV_ERROR( CV_StsBadArg, "Invalid or NULL first_frame parameter" );
if( !(first_frame->nChannels==3) )
CV_ERROR( CV_StsBadArg, "Need three channel image (RGB)" );
CV_CALL( bg_model = (CvGaussBGModel2*)cvAlloc( sizeof(*bg_model) ));
memset( bg_model, 0, sizeof(*bg_model) );
bg_model->type = CV_BG_MODEL_MOG2;
bg_model->release = (CvReleaseBGStatModel)icvReleaseGaussianBGModel2;
bg_model->update = (CvUpdateBGStatModel)icvUpdateGaussianBGModel2;
//init parameters
if( parameters == NULL )
{
/* These constants are defined in cvaux/include/cvaux.h: */
params.bRemoveForeground=0;
params.bShadowDetection = 1;
params.bPostFiltering=0;
params.minArea=CV_BGFG_MOG2_MINAREA;
//set parameters
// K - max number of Gaussians per pixel
params.nM = CV_BGFG_MOG2_NGAUSSIANS;//4;
// Tb - the threshold - n var
//pGMM->fTb = 4*4;
params.fTb = CV_BGFG_MOG2_STD_THRESHOLD*CV_BGFG_MOG2_STD_THRESHOLD;
// Tbf - the threshold
//pGMM->fTB = 0.9f;//1-cf from the paper
params.fTB = CV_BGFG_MOG2_BACKGROUND_THRESHOLD;
// Tgenerate - the threshold
params.fTg = CV_BGFG_MOG2_STD_THRESHOLD_GENERATE*CV_BGFG_MOG2_STD_THRESHOLD_GENERATE;//update the mode or generate new
//pGMM->fSigma= 11.0f;//sigma for the new mode
params.fSigma= CV_BGFG_MOG2_SIGMA_INIT;
// alpha - the learning factor
params.fAlphaT=1.0f/CV_BGFG_MOG2_WINDOW_SIZE;//0.003f;
// complexity reduction prior constant
params.fCT=CV_BGFG_MOG2_CT;//0.05f;
//shadow
// Shadow detection
params.nShadowDetection = CV_BGFG_MOG2_SHADOW_VALUE;//value 0 to turn off
params.fTau = CV_BGFG_MOG2_SHADOW_TAU;//0.5f;// Tau - shadow threshold
}
else
{
params = *parameters;
}
bg_model->params = params;
//allocate GMM data
w=first_frame->width;
h=first_frame->height;
size=w*h;
bg_model->data.nWidth=w;
bg_model->data.nHeight=h;
bg_model->data.nNBands=3;
bg_model->data.nSize=size;
//GMM for each pixel
bg_model->data.rGMM=(CvPBGMMGaussian*) malloc(size * params.nM * sizeof(CvPBGMMGaussian));
//used modes per pixel
bg_model->data.rnUsedModes = (unsigned char* ) malloc(size);
memset(bg_model->data.rnUsedModes,0,size);//no modes used
//prepare storages
CV_CALL( bg_model->background = cvCreateImage(cvSize(w,h), IPL_DEPTH_8U, first_frame->nChannels));
CV_CALL( bg_model->foreground = cvCreateImage(cvSize(w,h), IPL_DEPTH_8U, 1));
//for eventual filtering
CV_CALL( bg_model->storage = cvCreateMemStorage());
bg_model->countFrames = 0;
__END__;
if( cvGetErrStatus() < 0 )
{
CvBGStatModel* base_ptr = (CvBGStatModel*)bg_model;
if( bg_model && bg_model->release )
bg_model->release( &base_ptr );
else
cvFree( &bg_model );
bg_model = 0;
}
return (CvBGStatModel*)bg_model;
}
static void CV_CDECL
icvReleaseGaussianBGModel2( CvGaussBGModel2** _bg_model )
{
CV_FUNCNAME( "icvReleaseGaussianBGModel2" );
__BEGIN__;
if( !_bg_model )
CV_ERROR( CV_StsNullPtr, "" );
if( *_bg_model )
{
CvGaussBGModel2* bg_model = *_bg_model;
free (bg_model->data.rGMM);
free (bg_model->data.rnUsedModes);
cvReleaseImage( &bg_model->background );
cvReleaseImage( &bg_model->foreground );
cvReleaseMemStorage(&bg_model->storage);
memset( bg_model, 0, sizeof(*bg_model) );
cvFree( _bg_model );
}
__END__;
}
static int CV_CDECL
icvUpdateGaussianBGModel2( IplImage* curr_frame, CvGaussBGModel2* bg_model )
{
//int i, j, k, n;
int region_count = 0;
CvSeq *first_seq = NULL, *prev_seq = NULL, *seq = NULL;
float alpha,alphaInit;
bg_model->countFrames++;
alpha=bg_model->params.fAlphaT;
if (bg_model->params.bInit){
//faster initial updates
alphaInit=(1.0f/(2*bg_model->countFrames+1));
if (alphaInit>alpha)
{
alpha=alphaInit;
}
else
{
bg_model->params.bInit=0;
}
}
icvUpdatePixelBackgroundGMM(&bg_model->data,&bg_model->params,alpha,(unsigned char*)curr_frame->imageData,(unsigned char*)bg_model->foreground->imageData);
if (bg_model->params.bPostFiltering==1)
{
//foreground filtering
//filter small regions
cvClearMemStorage(bg_model->storage);
cvMorphologyEx( bg_model->foreground, bg_model->foreground, 0, 0, CV_MOP_OPEN, 1 );
cvMorphologyEx( bg_model->foreground, bg_model->foreground, 0, 0, CV_MOP_CLOSE, 1 );
cvFindContours( bg_model->foreground, bg_model->storage, &first_seq, sizeof(CvContour), CV_RETR_LIST );
for( seq = first_seq; seq; seq = seq->h_next )
{
CvContour* cnt = (CvContour*)seq;
if( cnt->rect.width * cnt->rect.height < bg_model->params.minArea )
{
//delete small contour
prev_seq = seq->h_prev;
if( prev_seq )
{
prev_seq->h_next = seq->h_next;
if( seq->h_next ) seq->h_next->h_prev = prev_seq;
}
else
{
first_seq = seq->h_next;
if( seq->h_next ) seq->h_next->h_prev = NULL;
}
}
else
{
region_count++;
}
}
bg_model->foreground_regions = first_seq;
cvZero(bg_model->foreground);
cvDrawContours(bg_model->foreground, first_seq, CV_RGB(0, 0, 255), CV_RGB(0, 0, 255), 10, -1);
return region_count;
}
else
{
return 1;
}
}
/* End of file. */
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