OpenCV API is very easy to manipulate image.
1. Read image from image file
2. Show the image in a window
- We use inread() to read an image to matrix which is called Mat in OpenCV
  Mat mat = inread()
- Use inshow() to show image in OpenCV  

/*
/Users/cat/myfile/bitbucket/opencv/loadimage.cpp
-----------------------------------------------------------------------
Wed Nov 28 16:03:20 2018 
-----------------------------------------------------------------------
open an image only
-----------------------------------------------------------------------
Compile: runopencv loadimage.cpp  => loadimage
Script:  $b/runopencv.sh
-----------------------------------------------------------------------
*/
int main(int argc, char** argv) {
 // Read the image file
 String path = "/Users/cat/myfile/bitbucket/image/dog1.jpeg";
 Mat image = imread(path);

 // Check for failure
 if (image.empty()) {
  cout << "Could not open or find the image" << endl;
  cout << "Image path=" << path << endl;
  cin.get(); //wait for any key press
  return -1;
 }

 String imageTitle = "Big dog"; //Name of the window

 namedWindow(imageTitle); // Create a window

 imshow(imageTitle, image); // Show our image inside the created window.

 waitKey(0); // Wait for any keystroke in the window

 destroyWindow(imageTitle); //destroy the created window

 return 0;
}