/*
平均背景法
*/
 
#include "highgui.h"
#include "cv.h"
#include<stdlib.h>
#include<stdio.h>
 
//為不同的臨時指針圖像和統計屬性創建指針
 
//Float, 3-channel images
IplImage* IavgF, * IdiffF, * IprevF, * IhiF, *IlowF;
 
IplImage* Iscratch, *Iscratch3;
 
//Float 1-channel images
 
IplImage* Igray1, * Igray2, * Igray3;
IplImage* Ilow1, * Ilow2, * Ilow3;
IplImage* Ihi1, *Ihi2, * Ihi3;
 
//Byte, 1-channel image
IplImage* Imask;
IplImage* Imaskt;
 
//Counts number of images learned for averaging later.
float Icount;
 
// 創建一個函數來給需要的所有臨時圖像分配內存
//為了方便，我們傳遞一幅圖像(來自視頻)作為大小參考來分配臨時圖像
 
void AllocateImages(IplImage* I)
{
 CvSize sz = cvGetSize(I);
 IavgF = cvCreateImage(sz, IPL_DEPTH_32F, 3);
 IdiffF = cvCreateImage(sz, IPL_DEPTH_32F,3);
 IprevF = cvCreateImage(sz, IPL_DEPTH_32F,3);
 IhiF = cvCreateImage(sz, IPL_DEPTH_32F, 3);
 IlowF = cvCreateImage(sz, IPL_DEPTH_32F,3);
 
 Ilow1 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Ilow2 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Ilow3 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Ihi1 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Ihi2 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Ihi3 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 cvZero(IavgF);
 cvZero(IdiffF);
 cvZero(IprevF);
 cvZero(IhiF);
 cvZero(IlowF);
 Icount = 0.00001;
 
 Iscratch = cvCreateImage(sz, IPL_DEPTH_32F,3);
 Iscratch3 = cvCreateImage(sz, IPL_DEPTH_32F,3);
 
 Igray1 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Igray2 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 Igray3 = cvCreateImage(sz, IPL_DEPTH_32F,1);
 
 Imask = cvCreateImage(sz, IPL_DEPTH_8U, 1);
 Imaskt = cvCreateImage(sz, IPL_DEPTH_8U,1);
 
 cvZero(Iscratch);
 cvZero(Iscratch3);
}
 
//學習累積背景圖像和每一幀圖像差值的絕對值
// Learn the background statistics for one more frame
// I is a color sample of the background, 3-channel, 8u
void accumulateBackground(IplImage *I)
{
 static int first = 1;
 cvCvtScale(I, Iscratch, 1, 0);
 if(!first)
 {
 cvAcc(Iscratch,IavgF);
 cvAbsDiff(Iscratch, IprevF, Iscratch3);
 cvAcc(Iscratch3,IdiffF);
 Icount += 1.0;
 }
 first = 0;
 cvCopy(Iscratch, IprevF);
}
 
//setHighThreshold和setLowThreshold都是基于每一幀圖像平均絕對差設置閾值的有效函數
void setHighThreshold(float scale)
{
 cvConvertScale(IdiffF, Iscratch, scale);
 cvAdd(Iscratch, IavgF, IhiF);
 cvSplit(IhiF, Ihi1, Ihi2, Ihi3, 0);
}
void setLowThreshold(float scale)
{
 cvConvertScale(IdiffF, Iscratch, scale);
 cvSub(IavgF, Iscratch, IlowF);
 cvSplit(IlowF, Ilow1, Ilow2, Ilow3, 0);
}
 
//當積累了足夠多的幀圖像之后，就將其轉化為一個背景的統計模型
//計算每一個像素的均值和方差觀測
void createModelsfromStats()
{
 cvConvertScale(IavgF, IavgF, (double)(1.0/Icount));
 cvConvertScale(IdiffF, IdiffF, (double)(1.0/Icount));
 
 //Make sure diff is always something
 
 cvAddS(IdiffF, cvScalar(1.0, 1.0, 1.0), IdiffF);
 setHighThreshold(7.0);
 setLowThreshold(6.0);
}
 
//有了背景模型，同時給出了高，低閾值，就能用它將圖像分割為前景和背景
// Create a binary: 0,255 mask where 255 means foregrond pixel
// I Input image, 3-channel, 8u
//Imask 
void backgroundDiff(IplImage* I)
{
 cvCvtScale(I, Iscratch, 1, 0);
 cvSplit(Iscratch, Igray1, Igray2, Igray3, 0);
 
 //Channel 1
 cvInRange(Igray1, Ilow1, Ihi1, Imask);
 
 //Channel 2
 cvInRange(Igray2, Ilow2, Ihi2, Imaskt);
 cvOr(Imask, Imaskt, Imask);
 
 //Channel 3
 cvInRange(Igray3, Ilow3, Ihi3, Imaskt);
 cvOr(Imask, Imaskt, Imask);
 
 //Finally, invert the result
 cvSubRS(Imask, cvScalar(255), Imask);
}
 
//完成背景建模后， 釋放內存
void DeallocateImage()
{
 cvReleaseImage(&IavgF);
 cvReleaseImage(&IdiffF);
 cvReleaseImage(&IprevF);
 cvReleaseImage(&IhiF);
 cvReleaseImage(&IlowF);
 cvReleaseImage(&Ilow1);
 cvReleaseImage(&Ilow2);
 cvReleaseImage(&Ilow3);
 cvReleaseImage(&Iscratch);
 cvReleaseImage(&Iscratch3);
 cvReleaseImage(&Igray1);
 cvReleaseImage(&Igray2);
 cvReleaseImage(&Igray3);
 cvReleaseImage(&Imaskt);
}
 
//主函數
int main()
{
 CvCapture* capture = cvCreateFileCapture("tree.avi");
 if(!capture)
 {
 return -1;
 }
 cvNamedWindow("win1");
 cvNamedWindow("win2");
 
 IplImage* rawImage = cvQueryFrame(capture);
 cvShowImage("win1", rawImage);
 
 AllocateImages(rawImage);
 int i = 0;
 while(1)
 {
 if(i <= 30)
 {
  accumulateBackground(rawImage);
  if(i == 30)
  {
  createModelsfromStats();
  }
 }
 else
 {
  backgroundDiff(rawImage);
 }
 cvShowImage("win2", Imask);
 
 if(cvWaitKey(33) == 27)
 {
  break;
 }
 if(!(rawImage = cvQueryFrame(capture)))
 {
  break;
 }
 cvShowImage("win1", rawImage);
 if(i == 56 || i == 63)
  cvWaitKey();
 i = i+1;
 }
 DeallocateImage();
 return 0;
}