OpenCV实现运动目标检测的函数

// 参数：
// img – 输入视频帧
// dst – 检测结果
void update_mhi( IplImage* img, IplImage* dst, int diff_threshold )
{
    double timestamp = clock()/100.; // get current time in seconds
    CvSize size = cvSize(img->width,img->height); // get current frame size
    int i, j, idx1, idx2;
    IplImage* silh;
    uchar val;
    float temp;
    IplImage* pyr = cvCreateImage( cvSize((size.width & -2)/2, (size.height & -2)/2), 8, 1 );
    CvMemStorage *stor;
    CvSeq *cont, *result, *squares;
    CvSeqReader reader;
    if( !mhi || mhi->width != size.width || mhi->height != size.height )
    {
        if( buf == 0 )
        {
            buf = (IplImage**)malloc(N*sizeof(buf[0]));
            memset( buf, 0, N*sizeof(buf[0]));
        }
        
        for( i = 0; i < N; i++ )
        {
            cvReleaseImage( &buf[i] );
            buf[i] = cvCreateImage( size, IPL_DEPTH_8U, 1 );
            cvZero( buf[i] );
        }
        cvReleaseImage( &mhi );
        mhi = cvCreateImage( size, IPL_DEPTH_32F, 1 );
        cvZero( mhi ); // clear MHI at the beginning
    } // end of if(mhi)
    cvCvtColor( img, buf[last], CV_BGR2GRAY ); // convert frame to grayscale
    idx1 = last;
    idx2 = (last + 1) % N; // index of (last - (N-1))th frame
    last = idx2;
    // 做帧差
    silh = buf[idx2];
    cvAbsDiff( buf[idx1], buf[idx2], silh ); // get difference between frames
    
    // 对差图像做二值化
    cvThreshold( silh, silh, 30, 255, CV_THRESH_BINARY ); // and threshold it
    
    cvUpdateMotionHistory( silh, mhi, timestamp, MHI_DURATION ); // update MHI
    cvCvtScale( mhi, dst, 255./MHI_DURATION,
      (MHI_DURATION - timestamp)*255./MHI_DURATION );    
    cvCvtScale( mhi, dst, 255./MHI_DURATION, 0 );    
    
    // 中值滤波，消除小的噪声
    cvSmooth( dst, dst, CV_MEDIAN, 3, 0, 0, 0 );
    
    // 向下采样，去掉噪声
    cvPyrDown( dst, pyr, 7 );
    cvDilate( pyr, pyr, 0, 1 ); // 做膨胀操作，消除目标的不连续空洞
    cvPyrUp( pyr, dst, 7 );
    //
    // 下面的程序段用来找到轮廓
    //
    // Create dynamic structure and sequence.
    stor = cvCreateMemStorage(0);
    cont = cvCreateSeq(CV_SEQ_ELTYPE_POINT, sizeof(CvSeq), sizeof(CvPoint) , stor);
    
    // 找到所有轮廓
    cvFindContours( dst, stor, &cont, sizeof(CvContour),
                    CV_RETR_LIST, CV_CHAIN_APPROX_SIMPLE, cvPoint(0,0));
/*
    for(;cont;cont = cont->h_next)
    {   
        // Number point must be more than or equal to 6 (for cvFitEllipse_32f).        
        if( cont->total < 6 )
            continue;
        // Draw current contour.
        cvDrawContours(img,cont,CV_RGB(255,0,0),CV_RGB(255,0,0),0,1, 8, cvPoint(0,0));
    } // end of for-loop: "cont"
*/
    // 直接使用CONTOUR中的矩形来画轮廓
    for(;cont;cont = cont->h_next)
    {
              CvRect r = ((CvContour*)cont)->rect;
              if(r.height * r.width > CONTOUR_MAX_AERA) // 面积小的方形抛弃掉
              {
                  cvRectangle( img, cvPoint(r.x,r.y),
                          cvPoint(r.x + r.width, r.y + r.height),
                          CV_RGB(255,0,0), 1, CV_AA,0);
              }
    }
    // free memory
    cvReleaseMemStorage(&stor);
    cvReleaseImage( &pyr );
}