C++ code conversion of Mat - c++

Question

I am trying to convert this second answer code into c++ , What I did is not giving me appropriate result , here is my code :
{
Mat img = imread("messi5.jpg");
int level_n = 2;
Mat p = Mat::zeros(img.cols*img.rows, 3, CV_32F);
vector<Mat> bgr;
cv::split(img, bgr);
//Divide each pixel color with 127 for level 2
for(int i=0; i<img.cols*img.rows; i++) {
p.at<float>(i,0) = bgr[0].data[i] / 127.0;
p.at<float>(i,1) = bgr[1].data[i] / 127.0;
p.at<float>(i,2) = bgr[2].data[i] / 127.0;
}
vector<Mat> Img2 = p[bgr];
Mat out;
cv::transform(img,out,p);
imshow ("output" , out);
}
What I didn't understand is how I put these colour's which I divided by 127 into Matrix , where I am going wrong?
Other way i am trying is
vector<Mat> bgr;
Mat blue , green , red;
cv::split(img, bgr);
blue = bgr[0]/127.0;
if (blue > 128)
{
blue = 255;
}
else
{
blue = 0;
}
same for red and green

Answer 1

Why don't just do it in place (for level 2):
Mat img = imread("messi5.jpg");
for(int i=0;i<img.rows;i++)
for(int j=0;j<img.cols;j++) {
cv::Vec3b p = img.at<cv::Vec3b>(i,j);
for(int k = 0;k < img.channels();k++)
p[k] = p[k] > 127 ? 255 : 0;
img.at<cv::Vec3b>(i,j) = p;
}
// do whatever you want with processed image img