How to access each pixel value of RGB image?

Question

I am trying to read RGB image. However, I can only access with Vec3b type, not each channel. I am sure what is the problem. Would like to help me out of misery?

imgMod = imread("rgb.png");

for (int iter_x = 0; iter_x < imgMod.cols; ++iter_x)
{
    for (int iter_y = 0; iter_y < imgMod.rows; ++iter_y)
    {
        cout << imgMod.at<cv::Vec3b>(iter_y, iter_x) << "\t";
        cout << imgMod.at<cv::Vec3b>(iter_y, iter_x)[0] << "\t";
        cout << imgMod.at<cv::Vec3b>(iter_y, iter_x)[1] << "\t";
        cout << imgMod.at<cv::Vec3b>(iter_y, iter_x)[2] << endl;
    }
}

Here is a result for pixel value of RGB image.

[153, 88, 81]          X     Q
[161, 94, 85]    。    ^     T
...

Answer 1

Your access is fine.
The type returned by the [] operator is char so the value gets printed as a char - a text character. Just cast it to int to see the grey value as an integer:

cout << int(imgMod.at<cv::Vec3b>(iter_y, iter_x)[0]) << "\t";

A (more readable and explicit) C++ way to do it would be this:

static_cast<int>(imgMod.at<cv::Vec3b>(iter_y, iter_x)[0]) << "\t";

Even more cool is this (obscure?) little trick - note the +:

cout << +imgMod.at<cv::Vec3b>(iter_y, iter_x)[0] << "\t";
//      ^