//代表一个2维的大小，包括长和宽。
template<typename _Tp> class Size_
{
public:
typedef _Tp value_type;
//! various constructors
Size_();
Size_(_Tp _width, _Tp _height);
Size_(const Size_& sz);
Size_(const CvSize& sz);
Size_(const CvSize2D32f& sz);
Size_(const Point_<_Tp>& pt);
Size_& operator = (const Size_& sz);
//! the area (width*height)
_Tp area() const;
//! conversion of another data type.
template<typename _Tp2> operator Size_<_Tp2>() const;
//! conversion to the old-style OpenCV types
operator CvSize() const;
operator CvSize2D32f() const;
_Tp width, height; // the width and the height
};