Image resized on loading using cv::imread opencv c++

I read a 768x1024 image, but on checking the image size shows as 384x512

Using OpenCV 3.4.6 and C++ 11

CODE:

cv::Mat img = cv::imread(argv[2], CV_8UC3); //768x1024
std::cout<< "Image: " << img.size << std::endl; //384x512

How to get the image dimensions correctly and convert the data float to subtract the mean BGR for VGG16?