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An doc says :

Template class for smart pointers with shared ownership.

A Ptr<t> pretends to be a pointer to an object of type T. Unlike an ordinary pointer, however, the object will be automatically cleaned up once all Ptr instances pointing to it are destroyed.

Ptr is similar to boost::shared_ptr that is part of the Boost library (http://www.boost.org/doc/libs/release/libs/smart_ptr/shared_ptr.htm) and std::shared_ptr from the C++11 standard.

This class provides the following advantages:

Default constructor, copy constructor, and assignment operator for an arbitrary C++ class or C structure. For some objects, like files, windows, mutexes, sockets, and others, a copy constructor or an assignment operator are difficult to define. For some other objects, like complex classifiers in OpenCV, copy constructors are absent and not easy to implement. Finally, some of complex OpenCV and your own data structures may be written in C. However, copy constructors and default constructors can simplify programming a lot. Besides, they are often required (for example, by STL containers). By using a Ptr to such an object instead of the object itself, you automatically get all of the necessary constructors and the assignment operator. O(1) complexity of the above-mentioned operations. While some structures, like std::vector, provide a copy constructor and an assignment operator, the operations may take a considerable amount of time if the data structures are large. But if the structures are put into a Ptr, the overhead is small and independent of the data size. Automatic and customizable cleanup, even for C structures. See the example below with FILE. Heterogeneous collections of objects. The standard STL and most other C++ and OpenCV containers can store only objects of the same type and the same size. The classical solution to store objects of different types in the same container is to store pointers to the base class (Base) instead but then you lose the automatic memory management. Again, by using Ptr<base> instead of raw pointers, you can solve the problem.

A Ptr is said to own a pointer - that is, for each Ptr there is a pointer that will be deleted once all Ptr instances that own it are destroyed. The owned pointer may be null, in which case nothing is deleted. Each Ptr also stores a pointer. The stored pointer is the pointer the Ptr pretends to be; that is, the one you get when you use Ptr::get or the conversion to T*. It's usually the same as the owned pointer, but if you use casts or the general shared-ownership constructor, the two may diverge: the Ptr will still own the original pointer, but will itself point to something else.

An doc says :

Template class for smart pointers with shared ownership.

A Ptr<t> pretends to be a pointer to an object of type T. Unlike an ordinary pointer, however, the object will be automatically cleaned up once all Ptr instances pointing to it are destroyed.

Ptr is similar to boost::shared_ptr that is part of the Boost library (http://www.boost.org/doc/libs/release/libs/smart_ptr/shared_ptr.htm) and std::shared_ptr from the C++11 standard.

This class provides the following advantages:...

Default constructor, copy constructor, and assignment operator for an arbitrary C++ class or C structure. For some objects, like files, windows, mutexes, sockets, and others, a copy constructor or an assignment operator are difficult to define. For some other objects, like complex classifiers in OpenCV, copy constructors are absent and not easy to implement. Finally, some of complex OpenCV and your own data structures may be written in C. However, copy constructors and default constructors can simplify programming a lot. Besides, they are often required (for example, by STL containers). By using a Ptr to such an object instead of the object itself, you automatically get all of the necessary constructors and the assignment operator. O(1) complexity of the above-mentioned operations. While some structures, like std::vector, provide a copy constructor and an assignment operator, the operations may take a considerable amount of time if the data structures are large. But if the structures are put into a Ptr, the overhead is small and independent of the data size. Automatic and customizable cleanup, even for C structures. See the example below with FILE. Heterogeneous collections of objects. The standard STL and most other C++ and OpenCV containers can store only objects of the same type and the same size. The classical solution to store objects of different types in the same container is to store pointers to the base class (Base) instead but then you lose the automatic memory management. Again, by using Ptr<base> instead of raw pointers, modify parameters you can solve the problem.use method setVarThreshold

An doc says :

Template class for smart pointers with shared ownership.

A Ptr<t> pretends to be a pointer to an object of type T. Unlike an ordinary pointer, however, the object will be automatically cleaned up once all Ptr instances pointing to it are destroyed.

Ptr is similar to boost::shared_ptr that is part of the Boost library (http://www.boost.org/doc/libs/release/libs/smart_ptr/shared_ptr.htm) and std::shared_ptr from the C++11 standard.

...

and to modify parameters you can use method setVarThreshold