The method to check that camera is moving or not(stop) using dense optical flow. (applied opencv, gpu version)

This post introduces how to check if the camera(video) is moving or not.


This method can be applied various fields.
This approach also means what scene is important or not.

To solve this problem, I used a dense optical flow.
I introduce dense optical flow on youtube.
http://www.youtube.com/watch?v=yAz1qrN6T_o
http://www.youtube.com/watch?v=iRMqH6y6JKU

and on my blog
http://feelmare.blogspot.kr/search/label/dense%20optical%20flow

In example source code..
The algorithm is checking that how much percent of area is moving?
And, check distance of each pixel movement. Smaller than the threshold value does not include in the movement percent.

Note, the example source code is made by gpu version.
#include < stdio.h>

#include < opencv2\opencv.hpp>
#include < opencv2/core/core.hpp>
#include < opencv2/highgui/highgui.hpp>
#include < opencv2\gpu\gpu.hpp>
#include < opencv2\nonfree\features2d.hpp >    



#ifdef _DEBUG        
#pragma comment(lib, "opencv_core249d.lib")
#pragma comment(lib, "opencv_imgproc249d.lib")   //MAT processing
#pragma comment(lib, "opencv_objdetect249d.lib") //HOGDescriptor
#pragma comment(lib, "opencv_gpu249d.lib")
#pragma comment(lib, "opencv_features2d249d.lib")
#pragma comment(lib, "opencv_highgui249d.lib")
#else
#pragma comment(lib, "opencv_core249.lib")
#pragma comment(lib, "opencv_imgproc249.lib")
#pragma comment(lib, "opencv_objdetect249.lib")
#pragma comment(lib, "opencv_gpu249.lib")
#pragma comment(lib, "opencv_features2d249.lib")
#pragma comment(lib, "opencv_highgui249.lib")
#endif 

using namespace std;
using namespace cv;

#define WIDTH_DENSE (80)
#define HEIGHT_DENSE (60)

#define DENSE_DRAW 0 //dense optical flow arrow drawing or not
#define GLOBAL_MOTION_TH1 1
#define GLOBAL_MOTION_TH2 70


float drawOptFlowMap_gpu (const Mat& flow_x, const Mat& flow_y, Mat& cflowmap, int step, float scaleX, float scaleY, int drawOnOff);


int main()
{
 //stream /////////////////////////////////////////////////
 VideoCapture stream1("C:\\videoSample\\medical\\HUV-03-14.wmv"); 

 //variables /////////////////////////////////////////////
 Mat O_Img; //Mat
 gpu::GpuMat O_Img_gpu; //GPU
 gpu::GpuMat R_Img_gpu_dense; //gpu dense resize
 gpu::GpuMat R_Img_gpu_dense_gray_pre; //gpu dense resize gray
 gpu::GpuMat R_Img_gpu_dense_gray; //gpu dense resize gray
 gpu::GpuMat flow_x_gpu, flow_y_gpu;
 Mat flow_x, flow_y;

 //algorithm *************************************
 //dense optical flow
 gpu::FarnebackOpticalFlow fbOF;
 

 //running once //////////////////////////////////////////
 if(!(stream1.read(O_Img))) //get one frame form video
 {
  printf("Open Fail !!\n");
  return 0; 
 }

  //for rate calucation
 float scaleX, scaleY;
 scaleX = O_Img.cols/WIDTH_DENSE;
 scaleY = O_Img.rows/HEIGHT_DENSE;

 O_Img_gpu.upload(O_Img); 
 gpu::resize(O_Img_gpu, R_Img_gpu_dense, Size(WIDTH_DENSE, HEIGHT_DENSE));
 gpu::cvtColor(R_Img_gpu_dense, R_Img_gpu_dense_gray_pre, CV_BGR2GRAY);


 //unconditional loop   ///////////////////////////////////
 while (true) {
  //reading
  if( stream1.read(O_Img) == 0) //get one frame form video   
   break;

  // ---------------------------------------------------
  //upload cou mat to gpu mat
  O_Img_gpu.upload(O_Img); 
  //resize
  gpu::resize(O_Img_gpu, R_Img_gpu_dense, Size(WIDTH_DENSE, HEIGHT_DENSE));
  //color to gray
  gpu::cvtColor(R_Img_gpu_dense, R_Img_gpu_dense_gray, CV_BGR2GRAY);
  
  //calculate dense optical flow using GPU version
  fbOF.operator()(R_Img_gpu_dense_gray_pre, R_Img_gpu_dense_gray, flow_x_gpu, flow_y_gpu);
  flow_x_gpu.download( flow_x );
  flow_y_gpu.download( flow_y );


  //calculate motion rate in whole image
  float motionRate = drawOptFlowMap_gpu(flow_x, flow_y, O_Img, 1, scaleX, scaleY, DENSE_DRAW);
  //update pre image
  R_Img_gpu_dense_gray_pre = R_Img_gpu_dense_gray.clone();



  //display "moving" or "stop" message on the image.
  if(motionRate > GLOBAL_MOTION_TH2 ) //if motion generate over than 70%, this algorithm consider that video is moving.
  {
   char TestStr[100] = "Moving!!";
   putText(O_Img, TestStr, Point(30,60), CV_FONT_NORMAL, 2, Scalar(0,0,255),3,2); //OutImg is Mat class;   
  }else{
   char TestStr[100] = "Stop!!";
   putText(O_Img, TestStr, Point(30,60), CV_FONT_NORMAL, 2, Scalar(255,0,0),3,2); //OutImg is Mat class; 
  }


  // show image ----------------------------------------
  imshow("Origin", O_Img);   

  // wait key
  if( cv::waitKey(100) > 30)
   break;
 }
}



float drawOptFlowMap_gpu (const Mat& flow_x, const Mat& flow_y, Mat& cflowmap, int step, float scaleX, float scaleY, int drawOnOff)
{
 double count=0;

 float countOverTh1 = 0;
 int sx,sy;
 for(int y = 0; y < HEIGHT_DENSE; y += step)
 {
  for(int x = 0; x < WIDTH_DENSE; x += step)
  {
   
   if(drawOnOff)
   {
    Point2f fxy;    
    fxy.x = cvRound( flow_x.at< float >(y, x)*scaleX + x*scaleX );   
    fxy.y = cvRound( flow_y.at< float >(y, x)*scaleY + y*scaleY );   
    line(cflowmap, Point(x*scaleX,y*scaleY), Point(fxy.x, fxy.y), CV_RGB(0, 255, 0));   
    circle(cflowmap, Point(fxy.x, fxy.y), 1, CV_RGB(0, 255, 0), -1);   
   }

   float xx = fabs(flow_x.at< float >(y, x) );
   float yy = fabs(flow_y.at< float >(y, x) );

   float xxyy = sqrt(xx*xx + yy*yy);
   if( xxyy > GLOBAL_MOTION_TH1 )
    countOverTh1 = countOverTh1 +1;
   
   count=count+1;
  }
 }
 return (countOverTh1 / count) * 100;

}


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