Opencv c++ read video frame imwrite images

這篇將讀取.mp4檔，將每個frame轉灰階並儲存為圖片。

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
#include <cv.h>
#include <string>
#include <sstream>
using namespace cv;
using namespace std;
int c=0;
string int2str(int &);

int main(int argc, char **argv){
 string s;

 VideoCapture cap("test.mp4"); // open the video file for reading

 if ( !cap.isOpened() )  // if not success, exit program
 {
   cout << "Cannot open the video file" << endl;
   return -1;
 }

 //cap.set(CV_CAP_PROP_POS_MSEC, 300); //start the video at 300ms

 double fps = cap.get(CV_CAP_PROP_FPS); //get the frames per seconds of the video

 cout << "Frame per seconds : " << fps << endl;

 namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"
 namedWindow("MyVideo_gray",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"
 while(1)
 {
  Mat frame;
  Mat Gray_frame;
  bool bSuccess = cap.read(frame); // read a new frame from video

  if (!bSuccess) //if not success, break loop
  {
   cout << "Cannot read the frame from video file" << endl;
   break;
  }
  cvtColor(frame, Gray_frame, CV_BGR2GRAY);
  s = int2str(c);
  //cout<<("%d\n",frame )<<endl;
  c++;
  imshow("MyVideo", frame); //show the frame in "MyVideo" window
  imshow("MyVideo_gray", Gray_frame);
  imwrite( "ig"+s+".jpg", Gray_frame );
  if(waitKey(30) == 27) //wait for 'esc' key press for 30 ms. If 'esc' key is pressed, break loop
  {
    cout << "esc key is pressed by user" << endl; 
    break; 
  }
 }

 return 0;

}

//int to string function
string int2str(int &i) {
 string s;
 stringstream ss(s);
 ss << i;
 return ss.str();
}

結果圖：