opencv
さまざまなメディアフォーマットの読み込みと保存

画像の読み込み

#include <highgui.h>

//...

cv::Mat img = cv::imread("img.jpg");

...

ビデオを読み込む

cv::VideoCapture使い方を見せてcv::VideoCapture 。ファイルからビデオを読み込む例を次に示します。

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/core/core.hpp"
#include <iostream>

using namespace cv;
VideoCapture videoSource;
Mat frame;
#define VIDEO_PATH "video.avi"

int main() 
{
    //Open video
    if (!videoSource.open(VIDEO_PATH))
    {            
        std::cout<<"Video not found at "<<VIDEO_PATH<<std::endl;
        return 1;     // Exit if fail
    }
    videoSource.set(CV_CAP_PROP_CONVERT_RGB, 1);
    
    int cameraWidth = videoSource.get(CV_CAP_PROP_FRAME_WIDTH);
    int cameraHeight = videoSource.get(CV_CAP_PROP_FRAME_HEIGHT);
    float cameraAspectRatio = cameraWidth / cameraHeight;

    std::cout <<"Camera resolution: " << cameraWidth<<", "<<cameraHeight<<" aspect ratio: "<<cameraAspectRatio<< std::endl;
    
    while(true)
    {
        videoSource >> frame;
        if(frame.empty())
            break;  
        //Resize frame
        cv::resize(frame, frame, cv::Size(320, 320 / cameraAspectRatio));
        imshow("frame", frame);
        waitKey(20);
    }
   waitKey(0);
   return 0;
}

ライブキャプチャ

cv::VideoCapture使用方法をWebカメラなどで表示します。ウェブカメラからフレームをキャプチャして表示します。次にコード例を示します。

#include <iostream> 

#include "opencv2/highgui/highgui.hpp"
#include "opencv2/imgproc/imgproc.hpp"
#include "opencv2/core/core.hpp"

using namespace cv;
VideoCapture videoSource;
Mat frame;

int main() 
{
    if(!videoSource.open(0)) //if more cameras available use 1,2,...
        return 1;
 
    while(true)
    {            
        videoSource >> frame;
        if(frame.empty())
            break;
        imshow("Webcam", frame); //or any kinf of precessing
        if(waitKey(1)==27)
            break;//stop capturing is ESC pressed
    }

   return 0;
}

動画を保存する

cv :: VideoWriterの使い方を見せてください。

#include "opencv2/highgui/highgui.hpp"
#include <iostream>

using namespace cv;
using namespace std;

int main(int argc, char* argv[])
{
    VideoCapture cap(0); // open the video camera no. 0

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

    namedWindow("MyVideo",CV_WINDOW_AUTOSIZE); //create a window called "MyVideo"
 
    double dWidth = cap.get(CV_CAP_PROP_FRAME_WIDTH); //get the width of frames of the video
    double dHeight = cap.get(CV_CAP_PROP_FRAME_HEIGHT); //get the height of frames of the video

    cout << "Frame Size = " << dWidth << "x" << dHeight << endl;

    Size frameSize(static_cast<int>(dWidth), static_cast<int>(dHeight));

    VideoWriter oVideoWriter ("D:/MyVideo.avi", CV_FOURCC('P','I','M','1'), 20, frameSize, true); //initialize the VideoWriter object 

    if ( !oVideoWriter.isOpened() ) //if not initialize the VideoWriter successfully, exit the program
   {
        cout << "ERROR: Failed to write the video" << endl;
        return -1;
   }

   while (1)
   {

    Mat frame;

    bool bSuccess = cap.read(frame); // read a new frame from video

    if (!bSuccess) //if not success, break loop
    {
         cout << "ERROR: Cannot read a frame from video file" << endl;
         break;
    }

    oVideoWriter.write(frame); //writer the frame into the file

    imshow("MyVideo", frame); //show the frame in "MyVideo" window

    if (waitKey(10) == 27) //wait for 'esc' key press for 30ms. If 'esc' key is pressed, break loop
   {
        cout << "esc key is pressed by user" << endl;
        break; 
   }
}

return 0;

}

画像を保存する

実際には、ライブキャプチャの例は画像をキャプチャするのに適しているので、画像をキャプチャしてフォルダに保存するために使用しています。

#include <fstream>
#include <string>

#include <opencv2/highgui/highgui.hpp>
#include <opencv2/core/core.hpp>
#include <opencv2/imgproc/imgproc.hpp>


int main() 
{
    std::stringstream file; // to write the file name 
    
    cv::VideoCapture cap(0); // create a capture object

    int counter = 0; // Create counter
    
    while(true) // infinite loop
    { 
        cv::Mat frame; // Create a object 
       
        cap.read(frame); // read the frame

        file << "/home/user/path_to_your_folder/image" << counter << ".jpg"; // file name

        cv::imwrite(file.str(), frame);
        
        counter++; // increment the counter
    }

   return 0;
}