reading_writing_images.cpp

#include <iostream>
#include <string>
#include <sstream>

using namespace std;

// OpenCV includes
#include <opencv2/core.hpp>
#include <opencv2/highgui.hpp>

using namespace cv;

int main(int argc, char** argv) {
    // Read images
    Mat color = imread("lena.jpg");
    Mat gray = imread("lena.jpg", CV_LOAD_IMAGE_GRAYSCALE);

    if (!color.data) {
        cout << "Could not open or find the image" << std::endl;
        return -1;
    }

    // Write images
    imwrite("lenaGray.jpg", gray);
    // Get same pixel with opencv function
    int myRow = color.cols - 1;
    int myCol = color.rows - 1;
    Vec3b pixel = color.at<Vec3b>(myRow, myCol);
    cout << "Pixel value (B,G,R): (" << (int)pixel[0] << "," << (int)pixel[1] << "," << (int)pixel[2] << ")" << endl;

    // show images
    imshow("Lena BGR", color);
    imshow("Lena Gray", gray);
    // wait for any key press
    waitKey(0);

    return 0;
}