OpenCV混合高斯模型函数注释说明

OpenCV混合高斯模型函数注释说明
一、cvaux.h
#define CV_BGFG_MOG_MAX_NGAUSSIANS   500
//高斯背景检测算法的默认参数设置
#define CV_BGFG_MOG_BACKGROUND_THRESHOLD     0.7     //高斯分布权重之和阈值
#define CV_BGFG_MOG_STD_THRESHOLD               2.5     //λ=2.5（99%）
#define CV_BGFG_MOG_WINDOW_SIZE                  200    //学习率α=1/win_size
#define CV_BGFG_MOG_NGAUSSIANS                   5       //k=5个混合高斯模型
#define CV_BGFG_MOG_WEIGHT_INIT                  0.05	 //初始权重
#define CV_BGFG_MOG_SIGMA_INIT                   30		 //初始标准差
#define CV_BGFG_MOG_MINAREA                     15.f		 //？？？

#define CV_BGFG_MOG_NCOLORS                      3       //颜色通道数
/************* CV_BG_STAT_MODEL_FIELDS()的宏定义**********************/ 
#define CV_BG_STAT_MODEL_FIELDS()                                                   
    int             type; 		//type of BG model
    CvReleaseBGStatModel release;  //                                               
    CvUpdateBGStatModel update;                                                     
    IplImage*       background;   /*8UC3 reference background image*/               
    IplImage*       foreground;   /*8UC1 foreground image*/                         
    IplImage**      layers;       /*8UC3 reference background image, can be null */ 
    int             layer_count;  /* can be zero */                                 
    CvMemStorage*   storage;      /*storage for foreground_regions?/              
    CvSeq*          foreground_regions /*foreground object contours*/
/*************************高斯背景模型参数结构体*************************/
typedef struct CvGaussBGStatModelParams
{    
    int     win_size;     //等于 1/alpha
    int     n_gauss;      //高斯模型的个数
    double  bg_threshold, std_threshold, minArea;	// bg_threshold：高斯分布权重之和阈值、std_threshold：2.5、minArea：？？？
    double  weight_init, variance_init;		//权重和方差
}CvGaussBGStatModelParams;
/**************************高斯分布模型结构体***************************/
typedef struct CvGaussBGValues
{
    int         match_sum;
    double      weight;
    double      variance[CV_BGFG_MOG_NCOLORS];
    double      mean[CV_BGFG_MOG_NCOLORS];
}
CvGaussBGValues;
typedef struct CvGaussBGPoint		
{
    CvGaussBGValues* g_values;
}
CvGaussBGPoint;
/*************************高斯背景模型结构体*************************/
typedef struct CvGaussBGModel
{
    CV_BG_STAT_MODEL_FIELDS();
    CvGaussBGStatModelParams   params;    
    CvGaussBGPoint*            g_point;    
    int                        countFrames;
}
CvGaussBGModel;
二、cvbgfg_gaussmix.cpp
//////////////////////////////////////////////////////////// cvCreateGaussianBGModel////////////////////////////////////////////////////////////////
功能：高斯背景模型变量bg_model初始化赋值
CV_IMPL CvBGStatModel* cvCreateGaussianBGModel( IplImage* first_frame, CvGaussBGStatModelParams* parameters)
{
    CvGaussBGModel* bg_model = 0;		//高斯背景状态模型变量
    
    CV_FUNCNAME( "cvCreateGaussianBGModel" );
    
    __BEGIN__;
    
    double var_init;
    CvGaussBGStatModelParams params;	//高斯背景状态模型参数变量
    int i, j, k, n, m, p;
    //初始化参数，如果参数为空，则进行初始化赋值
    if( parameters == NULL )
    {
        params.win_size = CV_BGFG_MOG_WINDOW_SIZE;		//学习率α=1/200=0.005
        params.bg_threshold = CV_BGFG_MOG_BACKGROUND_THRESHOLD;	//判断是否为背景点的阈值0.7
        params.std_threshold = CV_BGFG_MOG_STD_THRESHOLD;//标准阈值2.5
        params.weight_init = CV_BGFG_MOG_WEIGHT_INIT;		//权重值0.05
        params.variance_init = CV_BGFG_MOG_SIGMA_INIT*CV_BGFG_MOG_SIGMA_INIT; //方差30*30
        params.minArea = CV_BGFG_MOG_MINAREA;			//？？？
        params.n_gauss = CV_BGFG_MOG_NGAUSSIANS;		//高斯模型个数
    }
    else
    {
        params = *parameters;
    }
    
    if( !CV_IS_IMAGE(first_frame) )		//如果第一帧不是图像，则报错
        CV_ERROR( CV_StsBadArg, "Invalid or NULL first_frame parameter" );
    
    CV_CALL( bg_model = (CvGaussBGModel*)cvAlloc( sizeof(*bg_model) ));	//申请内存空间
    memset( bg_model, 0, sizeof(*bg_model) );
    bg_model->type = CV_BG_MODEL_MOG;		// CV_BG_MODEL_MOG高斯背景模型
    bg_model->release = (CvReleaseBGStatModel)icvReleaseGaussianBGModel;	//释放内存的函数指针
    bg_model->update = (CvUpdateBGStatModel)icvUpdateGaussianBGModel;	//更新高斯模型的函数指针    
bg_model->params = params;

    //申请内存空间
    CV_CALL( bg_model->g_point = (CvGaussBGPoint*)cvAlloc(sizeof(CvGaussBGPoint)*
        ((first_frame->width*first_frame->height) + 256)));		//256?
    
    CV_CALL( bg_model->background = cvCreateImage(cvSize(first_frame->width,
        first_frame->height), IPL_DEPTH_8U, first_frame->nChannels));
    CV_CALL( bg_model->foreground = cvCreateImage(cvSize(first_frame->width,
        first_frame->height), IPL_DEPTH_8U, 1));
    
    CV_CALL( bg_model->storage = cvCreateMemStorage());
    
    //初始化
    var_init = 2 * params.std_threshold * params.std_threshold;		//初始化方差
    CV_CALL( bg_model->g_point[0].g_values =
        (CvGaussBGValues*)cvAlloc( sizeof(CvGaussBGValues)*params.n_gauss*
        (first_frame->width*first_frame->height + 128)));			//128?
	//n：表示像素点的索引值
	//p：表示当前像素对应颜色通道的首地址
	// g_point[]：对应像素点、g_values[]：对应高斯模型、variance[]和 mean[]：对应颜色通道
    for( i = 0, p = 0, n = 0; i < first_frame->height; i++ )		//行
    {
        for( j = 0; j < first_frame->width; j++, n++ )		//列
        {
            bg_model->g_point[n].g_values = bg_model->g_point[0].g_values + n*params.n_gauss;//每个像素点的第一个高斯模型的地址（每个像素对应n_gauss个高斯分布模型）

		   //初始化第一个高斯分布模型的参数
            bg_model->g_point[n].g_values[0].weight = 1;    //取较大权重，此处设置为1
            bg_model->g_point[n].g_values[0].match_sum = 1;//高斯函数被匹配的次数（？？？）
            for( m = 0; m < first_frame->nChannels; m++)	   //对各颜色通道的方差和均值赋值
            {
                bg_model->g_point[n].g_values[0].variance[m] = var_init;	//初始化较大的方差
                bg_model->g_point[n].g_values[0].mean[m] = (unsigned char)first_frame->imageData[p + m];														//赋值为当前像素值
            }

		   //初始化剩下的高斯分布模型的参数
            for( k = 1; k < params.n_gauss; k++)
            {
                bg_model->g_point[n].g_values[k].weight = 0;//各高斯分布取相等且较小权重值，此处取0
                bg_model->g_point[n].g_values[k].match_sum = 0;
                for( m = 0; m < first_frame->nChannels; m++)
{
                    bg_model->g_point[n].g_values[k].variance[m] = var_init; //初始化较大的方差
                    bg_model->g_point[n].g_values[k].mean[m] = 0;		  //赋值0
                }
            }
            p += first_frame->nChannels;
        }
    }
    
    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;
}
////////////////////////////////////////////////////////// icvUpdateGaussianBGModel ///////////////////////////////////////////////////////////////
功能：对高斯背景模型变量bg_model进行更新
static int CV_CDECL icvUpdateGaussianBGModel( IplImage* curr_frame, CvGaussBGModel*  bg_model )
{
    int i, j, k;
    int region_count = 0;
    CvSeq *first_seq = NULL, *prev_seq = NULL, *seq = NULL;
    
    bg_model->countFrames++;
    
    for( i = 0; i < curr_frame->height; i++ )	//行
    {
        for( j = 0; j < curr_frame->width; j++ )	//列
        {
            int match[CV_BGFG_MOG_MAX_NGAUSSIANS];
            double sort_key[CV_BGFG_MOG_MAX_NGAUSSIANS];
            const int nChannels = curr_frame->nChannels;	//通道数目
            const int n = i*curr_frame->width+j;			//像素索引值
            const int p = n*curr_frame->nChannels;		//像素点颜色通道的首地址
            
            // A few short cuts
            CvGaussBGPoint* g_point = &bg_model->g_point[n];
            const CvGaussBGStatModelParams bg_model_params = bg_model->params;
            double pixel[4];
            int no_match;
            
            for( k = 0; k < nChannels; k++ )		//拷贝各通道颜色分量值
                pixel[k] = (uchar)curr_frame->imageData[p+k];
            
            no_match = icvMatchTest( pixel, nChannels, match, g_point, &bg_model_params );
		   //判断高斯背景模型更新帧数是否达到设置值win_size（？？？）
（初始更新阶段和一般更新阶段在更新处理过程中是不同的，其中定义初始更新阶段为帧数小于win_size）
            if( bg_model->countFrames == bg_model->params.win_size )	//一般更新阶段
            {
                icvUpdateFullWindow( pixel, nChannels, match, g_point, &bg_model->params );
                if( no_match == -1)
                    icvUpdateFullNoMatch( curr_frame, p, match, g_point, &bg_model_params );
            }
            else
            {
                icvUpdatePartialWindow( pixel, nChannels, match, g_point, &bg_model_params );
                if( no_match == -1)
                    icvUpdatePartialNoMatch( pixel, nChannels, match, g_point, &bg_model_params );
            }
            icvGetSortKey( nChannels, sort_key, g_point, &bg_model_params );
            icvInsertionSortGaussians( g_point, sort_key, (CvGaussBGStatModelParams *)&bg_model_params );
            icvBackgroundTest( nChannels, n, p, match, bg_model );
        }
    }
    
    //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;
}
//////////////////////////////////////////////////////////// icvMatchTest ////////////////////////////////////////////////////////////////
功能：将当前像素与个高斯分布进行匹配判断，如果匹配成功，则返回相应高斯分布的索引值
static int icvMatchTest( double* src_pixel, int nChannels, int* match,
                         const CvGaussBGPoint* g_point,
                         const CvGaussBGStatModelParams *bg_model_params )
{
    int k;
    int matchPosition=-1;
    for ( k = 0; k < bg_model_params->n_gauss; k++) match[k]=0;	//高斯分布匹配标识数组初始化置0
    
for ( k = 0; k < bg_model_params->n_gauss; k++)
{
        double sum_d2 = 0.0;
        double var_threshold = 0.0;
        for(int m = 0; m < nChannels; m++)	//计算当前高斯分布各通道均值与像素点各通道值相减
{
            double d = g_point->g_values[k].mean[m]- src_pixel[m];
            sum_d2 += (d*d);
            var_threshold += g_point->g_values[k].variance[m];
        }  //difference < STD_LIMIT*STD_LIMIT or difference**2 < STD_LIMIT*STD_LIMIT*VAR
        var_threshold = _model_params->std_threshold*bg_model_params->std_threshold*var_threshold;
//匹配方程为：或者
        if(sum_d2 < var_threshold)
{
            match[k] = 1;		//匹配时标识置1
            matchPosition = k;	//存储匹配的高斯分布索引值
            break;				//一旦匹配，就终止与后续高斯分布的匹配
        }
    }
    
    return matchPosition;		//返回匹配上的高斯分布索引值
}
//////////////////////////////////////////////////// icvUpdateFullWindow ////////////////////////////////////////////////////////////
功能：更新各高斯分布的权重值（对于匹配上的高斯分布要增大权值，其余的减小权值），如果存在匹配上的高斯分布，还要更新其均值和方差。
static void icvUpdateFullWindow( double* src_pixel, int nChannels, int* match,
                                 CvGaussBGPoint* g_point,
                                 const CvGaussBGStatModelParams *bg_model_params )
{
    const double learning_rate_weight = (1.0/(double)bg_model_params->win_size);	//学习率α
for(int k = 0; k < bg_model_params->n_gauss; k++)
{
	   //若match[k]=0，则权重ω的更新公式：
	   //若match[k]=0，则权重ω的更新公式：
        g_point->g_values[k].weight = 
g_point->g_values[k].weight + (learning_rate_weight*((double)match[k] -g_point->g_values[k].weight));
        if(match[k])			//更新匹配的高斯分布的参数
{
            //参数学习率
double learning_rate_gaussian =         (double)match[k]/(g_point->g_values[k].weight*(double)bg_model_params->win_size);	
            for(int m = 0; m < nChannels; m++)
{
                const double tmpDiff = src_pixel[m] - g_point->g_values[k].mean[m];
			  //均值μ更新公式为：
                g_point->g_values[k].mean[m] = 
g_point->g_values[k].mean[m] +(learning_rate_gaussian * tmpDiff);
			 //方差更新公式为：
                g_point->g_values[k].variance[m] = g_point->g_values[k].variance[m]+
                    (learning_rate_gaussian*((tmpDiff*tmpDiff) - g_point->g_values[k].variance[m]));
            }
        }
    }
}
//////////////////////////////////////////////////// icvUpdateFullNoMatch ////////////////////////////////////////////////////////////
功能：当前像素点与所有高斯分布都不匹配时，需要将比值最小的高斯分布替换为新的高斯分布（权值小、方差大），其余的高斯分布保持原来的均值和方差，但权值需要减小。
static void icvUpdateFullNoMatch( IplImage* gm_image, int p, int* match,
                                  CvGaussBGPoint* g_point,
                                  const CvGaussBGStatModelParams *bg_model_params)
{
    int k, m;
    double alpha;
    int match_sum_total = 0;

    //new value of last one
    g_point->g_values[bg_model_params->n_gauss - 1].match_sum = 1;	//将新的高斯分布的match_sum置为1
    
    //get sum of all but last value of match_sum    
    for( k = 0; k < bg_model_params->n_gauss ; k++ )
        match_sum_total += g_point->g_values[k].match_sum;
    
	//设置新的高斯分布的参数
    g_point->g_values[bg_model_params->n_gauss - 1].weight = 1./(double)match_sum_total; //给新的高斯分布设置一个较小的权值，即1.0/ match_sum_total
    for( m = 0; m < gm_image->nChannels ; m++ )
    {
        // first pass mean is image value
        g_point->g_values[bg_model_params->n_gauss - 1].variance[m] = bg_model_params->variance_init;	//初始化一个较大的方差
        g_point->g_values[bg_model_params->n_gauss - 1].mean[m] = (unsigned char)gm_image->imageData[p + m]; //将当前像素值作为均值
    }
    
//更新其余高斯分布的参数
    alpha = 1.0 - (1.0/bg_model_params->win_size);
    for( k = 0; k < bg_model_params->n_gauss - 1; k++ )
{
	   //更新权值的公式为：
        g_point->g_values[k].weight *= alpha;
        if( match[k] )	//对于匹配的高斯分布，权值更新公式为
            g_point->g_values[k].weight += alpha;
    }
}
//////////////////////////////////////////////////// icvUpdatePartialWindow ////////////////////////////////////////////////////////////
功能：更新各高斯分布的权重值（对于匹配上的高斯分布要增大权值，其余的减小权值），如果存在匹配上的高斯分布，还要更新其均值和方差。
static void icvUpdatePartialWindow( double* src_pixel, int nChannels, int* match, CvGaussBGPoint* g_point, const CvGaussBGStatModelParams *bg_model_params )
{
    int k, m;
    int window_current = 0;
    
    for( k = 0; k < bg_model_params->n_gauss; k++ )
        window_current += g_point->g_values[k].match_sum;
    
    for( k = 0; k < bg_model_params->n_gauss; k++ )
    {
        g_point->g_values[k].match_sum += match[k];
        double learning_rate_weight = (1.0/((double)window_current + 1.0)); //increased by one since sum
        g_point->g_values[k].weight = g_point->g_values[k].weight +
            (learning_rate_weight*((double)match[k] - g_point->g_values[k].weight));
        
        if( g_point->g_values[k].match_sum > 0 && match[k] )
        {
            double learning_rate_gaussian = (double)match[k]/((double)g_point->g_values[k].match_sum);
            for( m = 0; m < nChannels; m++ )
            {
                const double tmpDiff = src_pixel[m] - g_point->g_values[k].mean[m];
                g_point->g_values[k].mean[m] = g_point->g_values[k].mean[m] +
                    (learning_rate_gaussian*tmpDiff);
                g_point->g_values[k].variance[m] = g_point->g_values[k].variance[m]+
                    (learning_rate_gaussian*((tmpDiff*tmpDiff) - g_point->g_values[k].variance[m]));
            }
        }
    }
}