extractFrames.cpp

#include <opencv2/core/core.hpp>
#include <opencv2/highgui/highgui.hpp>
#include <opencv2/imgproc/imgproc.hpp>
#include <iostream>
#include <string>
#include <stdio.h>
#include <sys/stat.h>

using namespace std;
using namespace cv;

//#define DISPLAY

string num2str(int i)
{
	char ss[10];
	sprintf(ss, "%05d", i);
	return ss;
}


int main(int argc, char* argv[])
{
	std::string VideoFile;
	std::string SaveDir = "resultFrames";

	if (argc == 2) {
		VideoFile = argv[1];
	}
	else if (argc == 3) {
		VideoFile = argv[1];
		SaveDir = argv[2];
	}
	else {
		cout << "Usage: " << argv[0]
			<< " VideoFile [FrameSavedDir]" << endl;
		return -1;
	}

	// Open Video
	VideoCapture capture(VideoFile.c_str());
	if (!capture.isOpened())
		cout << "fail to open!" << endl;

	long totalFrameNumber = capture.get(CV_CAP_PROP_FRAME_COUNT);
	std::cout << "Total frames[ " << totalFrameNumber << " ]" << std::endl;


	//set start frame
	long frameToStart = 0;
	capture.set(CV_CAP_PROP_POS_FRAMES, frameToStart);
	cout << "The start frame to extract: " << frameToStart << endl;


	//set stop frame
	//TODO
	//long frameToStop = 20;

	//get frame rate
	double rate = capture.get(CV_CAP_PROP_FPS);
	cout << "The frame rate is: " << rate << endl;

	//flag to control stop reading
	bool stop = false;

	Mat frame;
	std::string img_name;
#ifdef DISPLAY
	//Display the extracted frame
	namedWindow("Extracted frame");
	//the internel time between two frames
	int delay = 1000 / rate;
#endif

	long currentFrame = frameToStart;

#ifdef DISPLAY
	// add a filter
	int kernel_size = 3;
	Mat kernel = Mat::ones(kernel_size,
		kernel_size, CV_32F) / (float)(kernel_size*kernel_size);
#endif

	while (!stop)
	{
		//read a frame
		if (!capture.read(frame))
		{
			goto RELEASE;
		}
		//img_name = SaveDir + "/" + std::to_string(currentFrame) + ".jpg"; num2str
		img_name = SaveDir + "/" + num2str(currentFrame) + ".jpg";
		cv::imwrite(img_name.c_str(), frame);

#ifdef DISPLAY
		imshow("Extracted frame", frame);
		filter2D(frame, frame, -1, kernel);
		imshow("after filter", frame);
#endif
		if (((currentFrame + 1) % 100) == 0) cout << "-" << endl;
		else cout << "-";

#ifdef DISPLAY
		// when delay ≤ 0, wait forever, else wait delay ms
		int c = waitKey(delay);
		// click ESC or get the stop frame, exit
		if ((char)c == 27) {
			stop = true;
		}
		// click key to wait extracting the next frame
		if (c >= 0) {
			waitKey(0);
		}
#endif
		currentFrame++;

	}
	//release
RELEASE:
	cout << "\nRead total frames: " << currentFrame - frameToStart << endl;
	cout << "please check the results in dir: " << SaveDir << endl;
	capture.release();
	waitKey(0);
	return 0;
}

usage:

extractFrames.exe  test.mp4  C:\saveDir\