Namespace cv and Function Naming
================================

.. highlight:: cpp


All the newly introduced classes and functions are placed into 
``cv``
namespace. Therefore, to access this functionality from your code, use 
``cv::``
specifier or 
``"using namespace cv;"``
directive:



::


    
    #include "cv.h"
    
    ...
    cv::Mat H = cv::findHomography(points1, points2, cv::RANSAC, 5);
    ...
    

..

or



::


    
    #include "cv.h"
    
    using namespace cv;
    
    ...
    Mat H = findHomography(points1, points2, RANSAC, 5 );
    ...
    

..

It is probable that some of the current or future OpenCV external names conflict with STL
or other libraries, in this case use explicit namespace specifiers to resolve the name conflicts:



::


    
    Mat a(100, 100, CV_32F);
    randu(a, Scalar::all(1), Scalar::all(std::rand()
    cv::log(a, a);
    a /= std::log(2.);
    

..

For the most of the C functions and structures from OpenCV 1.x you may find the direct counterparts in the new C++ interface. The name is usually formed by omitting 
``cv``
or 
``Cv``
prefix and turning the first letter to the low case (unless it's a own name, like Canny, Sobel etc). In case when there is no the new-style counterpart, it's possible to use the old functions with the new structures, as shown the first sample in the chapter.