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

using namespace cv;
using namespace std;

int main( int argc, char** argv )
{
    Mat image;
    image = imread("pic.jpg", IMREAD_COLOR);   // Read the file
    if(! image.data )                              // Check for invalid input
    {
        cout <<  "Could not open or find the image" << std::endl ;
        return -1;
    }
    for(int i = 0; i < image.rows; i++)
    {
        //pointer to 1st pixel in row
        Vec3b* p = image.ptr<Vec3b>(i);
        for (int j = 0; j < image.cols; j++)
            for (int ch = 0; ch < 3; ch++)
                p[j][ch]  // – channel ch
    }
    imwrite("pic2.jpg",image);

    //show image
    namedWindow( "Display window", WINDOW_AUTOSIZE );// Create a window for display.
    imshow( "Display window", image );                   // Show our image inside it.
    waitKey(0);                                          // Wait for a keystroke in the window
    return 0;
}