// 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 );
}