如何提取视频帧并将它们另存为使用c + +的图像

Question

我现在试图将视频文件的帧保存到我的电脑上的图像。我正在使用Visual Studio 2010和opencv 2.3.1。在这段代码中（如下图所示），它可以保存图像序列的帧，但对于视频文件，我无法保存帧。 问题专门似乎是在这里： 在vidoeprocessing的功能（）

string imageToSave =("output_MOG_" + frameNumberString + ".png"); 
    bool saved = imwrite(imageToSave,fgMaskMOG); 
    if(!saved) { 
    cerr << "Unable to save " << imageToSave << endl; 
     } 

任何一个可以帮助解决这个问题？
在此先感谢。

我的代码是这样的：

//opencv 
#include < opencv2/opencv.hpp> 
#include < opencv2/core/core.hpp> 
#include < opencv2/highgui/highgui.hpp> 
#include < opencv2/video/background_segm.hpp> 
//#include <opencv2/imgcodecs.hpp> 
#include <opencv2/imgproc/imgproc.hpp> 
//#include "opencv2/videoio.hpp" 
    #include <opencv2/video/video.hpp> 
//C 
#include <stdio.h> 
//C++ 
#include <iostream> 
#include <sstream> 

using namespace cv; 
using namespace std; 

     // Global variables 
    Mat frame; //current frame 
Mat fgMaskMOG; //fg mask fg mask generated by MOG method 
Ptr<BackgroundSubtractor> pMOG; //MOG Background subtractor 
int keyboard; //input from keyboard 

/** Function Headers */ 
void help(); 
void processVideo(char* videoFilename); 
void processImages(char* firstFrameFilename); 

void help() 
{ 
cout 
    << "--------------------------------------------------------------------- -----" << endl 
<< "This program shows how to use background subtraction methods provided by " << endl 
<< " OpenCV. You can process both videos (-vid) and images (-img)."    << endl 
                       << endl 
<< "Usage:"                  << endl 
<< "./bs {-vid <video filename>|-img <image filename>}"       << endl 
<< "for example: ./bs -vid video.avi"           << endl 
<< "or: ./bs -img /data/images/1.png"           << endl 
<< "--------------------------------------------------------------------------" << endl 
<< endl; 
} 

/** 
* @function main 
*/ 
int main(int argc, char* argv[]) 
{ 


    //print help information 
    help(); 

    //check for the input parameter correctness 
    if(argc != 3) { 
    cerr <<"Incorret input list" << endl; 
    cerr <<"exiting..." << endl; 
    return EXIT_FAILURE; 
} 


//create GUI windows 
namedWindow("Frame"); 
namedWindow("FG Mask MOG "); 

//create Background Subtractor objects 
pMOG = new BackgroundSubtractorMOG(); 
if(strcmp(argv[1], "-vid") == 0) { 
    //input data coming from a video 
    processVideo(argv[2]); 
} 
else if(strcmp(argv[1], "-img") == 0) { 
    //input data coming from a sequence of images 
    processImages(argv[2]); 
} 
else { 
    //error in reading input parameters 
    cerr <<"Please, check the input parameters." << endl; 
    cerr <<"Exiting..." << endl; 
    return EXIT_FAILURE; 
} 
//destroy GUI windows 
destroyAllWindows(); 
return EXIT_SUCCESS; 
} 

//function processVideo 

void processVideo(char* videoFilename) { 
    //create the capture object 
    VideoCapture capture(videoFilename); 
    if(!capture.isOpened()){ 
    //error in opening the video input 
    cerr << "Unable to open video file: " << videoFilename << endl; 
    exit(EXIT_FAILURE); 
} 
//read input data. ESC or 'q' for quitting 
    while((char)keyboard != 'q' && (char)keyboard != 27){ 
    //read the current frame 
    if(!capture.read(frame)) { 
     cerr << "Unable to read next frame." << endl; 
     cerr << "Exiting..." << endl; 
     exit(EXIT_FAILURE); 
    } 

    //update the background model 
    pMOG->operator()(frame, fgMaskMOG,0.9); 
    //get the frame number and write it on the current frame 

    stringstream ss; 
    rectangle(frame, cv::Point(10, 2), cv::Point(100,20), 
       cv::Scalar(255,255,255), -1); 
    ss << capture.get(CV_CAP_PROP_POS_FRAMES); 
    string frameNumberString = ss.str(); 

    putText(frame, frameNumberString.c_str(), cv::Point(15, 15), 
      FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0)); 
    //show the current frame and the fg masks 
    imshow("Frame", frame); 
    imshow("FG Mask MOG ", fgMaskMOG); 
    //get the input from the keyboard 
    keyboard = waitKey(30); 
} 

/* 
string imageToSave =("output_MOG_" + frameNumberString + ".bmp"); 
    bool saved = imwrite(imageToSave,fgMaskMOG); 
    if(!saved) { 
    cerr << "Unable to save " << imageToSave << endl; 
     } 
     */ 


//delete capture object 
capture.release(); 
} 

/** 
* @function processImages 
*/ 
void processImages(char* fistFrameFilename) { 
    //read the first file of the sequence 
    frame = imread(fistFrameFilename); 
    if(frame.empty()){ 
    //error in opening the first image 
    cerr << "Unable to open first image frame: " << fistFrameFilename <<  endl; 
    exit(EXIT_FAILURE); 
} 
//current image filename 
string fn(fistFrameFilename); 
//read input data. ESC or 'q' for quitting 
while((char)keyboard != 'q' && (char)keyboard != 27){ 
    //update the background model 
    pMOG->operator()(frame, fgMaskMOG,0.9); 
    //get the frame number and write it on the current frame 
    size_t index = fn.find_last_of("/"); 
    if(index == string::npos) { 
     index = fn.find_last_of("\\"); 
    } 
    size_t index2 = fn.find_last_of("."); 
    string prefix = fn.substr(0,index+1); 
    string suffix = fn.substr(index2); 
    string frameNumberString = fn.substr(index+1, index2-index-1); 
    istringstream iss(frameNumberString); 
    int frameNumber = 0; 
    iss >> frameNumber; 
    rectangle(frame, cv::Point(10, 2), cv::Point(100,20), 
       cv::Scalar(255,255,255), -1); 
    putText(frame, frameNumberString.c_str(), cv::Point(15, 15), 
      FONT_HERSHEY_SIMPLEX, 0.5 , cv::Scalar(0,0,0)); 
    //show the current frame and the fg masks 
    imshow("Frame", frame); 
    imshow("FG Mask MOG ", fgMaskMOG); 
    //get the input from the keyboard 
    keyboard = waitKey(30); 
    //search for the next image in the sequence 
    ostringstream oss; 
    oss << (frameNumber + 1); 
    string nextFrameNumberString = oss.str(); 
    string nextFrameFilename = prefix + nextFrameNumberString + suffix; 
    //read the next frame 
    frame = imread(nextFrameFilename); 
    if(frame.empty()){ 
     //error in opening the next image in the sequence 
     cerr << "Unable to open image frame: " << nextFrameFilename << endl; 
     exit(EXIT_FAILURE); 
    } 
    //update the path of the current frame 
    fn.assign(nextFrameFilename); 

    // save subtracted images 
    string imageToSave =("output_MOG_" + frameNumberString + ".png"); 
    bool saved = imwrite(imageToSave,fgMaskMOG); 
    if(!saved) { 
    cerr << "Unable to save " << imageToSave << endl; 
     } 
} 
} 

Answer 1

这是使用网络摄像头一个小样本。你可以很容易地适应它使用视频：

#include "opencv2/opencv.hpp" 
using namespace cv; 

int main(int, char**) 
{ 
    VideoCapture cap(0); // open the default camera 
    if (!cap.isOpened()) // check if we succeeded 
     return -1; 

    Ptr<BackgroundSubtractor> pMOG = new BackgroundSubtractorMOG2(); 

    Mat fg_mask; 
    Mat frame; 
    int count = -1; 

    for (;;) 
    { 
     // Get frame 
     cap >> frame; // get a new frame from camera 

     // Update counter 
     ++count; 

     // Background subtraction 
     pMOG->operator()(frame, fg_mask); 

     imshow("frame", frame); 
     imshow("fg_mask", fg_mask); 

     // Save foreground mask 
     string name = "mask_" + std::to_string(count) + ".png"; 
     imwrite("D:\\SO\\temp\\" + name, fg_mask); 

     if (waitKey(1) >= 0) break; 
    } 
    // the camera will be deinitialized automatically in VideoCapture destructor 
    return 0; 
}