OpenCV笔记（Ptr）
//OpenCV中使用的智能指针。类似于std::smart_ptr,但是在OpenCV中可以用Ptr轻松管理各种类型的指针。
//可以用Ptr<MyObjectType> ptr代替MyObjectType* ptr,MyObjectType可以是C的结构体或C++的类，
//如果没有自动析构的函数，需要实现
//template<> void Ptr<MyObjectType>::delete_obj() { call_destructor_func(obj); }
//如果C++类中有析构函数，可以不用实现。
template<typename _Tp> class Ptr
{
public:
//! empty constructor
Ptr();
//! take ownership of the pointer. The associated reference counter is allocated and set to 1
Ptr(_Tp* _obj);
//! calls release()
~Ptr();
//! copy constructor. Copies the members and calls addref()
Ptr(const Ptr& ptr);
template<typename _Tp2> Ptr(const Ptr<_Tp2>& ptr);
//! copy operator. Calls ptr.addref() and release() before copying the members
Ptr& operator = (const Ptr& ptr);
//! increments the reference counter
void addref();
//! decrements the reference counter. If it reaches 0, delete_obj() is called
void release();
//! deletes the object. Override if needed
void delete_obj();
//! returns true iff obj==NULL
bool empty() const;
//! cast pointer to another type
template<typename _Tp2> Ptr<_Tp2> ptr();
template<typename _Tp2> const Ptr<_Tp2> ptr() const;
//! helper operators making "Ptr<T> ptr" use very similar to "T* ptr".
_Tp* operator -> ();
const _Tp* operator -> () const;
operator _Tp* ();
operator const _Tp*() const;
_Tp* obj; //< the object pointer.
int* refcount; //< the associated reference counter
};
