include/opencv2/core/traits.hpp

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#ifndef OPENCV_CORE_TRAITS_HPP
#define OPENCV_CORE_TRAITS_HPP

#include "opencv2/core/cvdef.h"

namespace cv
{

//#define OPENCV_TRAITS_ENABLE_DEPRECATED

//! @addtogroup core_basic
//! @{

/** @brief Template "trait" class for OpenCV primitive data types.

@note Deprecated. This is replaced by "single purpose" traits: traits::Type and traits::Depth

A primitive OpenCV data type is one of unsigned char, bool, signed char, unsigned short, signed
short, int, float, double, or a tuple of values of one of these types, where all the values in the
tuple have the same type. Any primitive type from the list can be defined by an identifier in the
form CV_\<bit-depth\>{U|S|F}C(\<number_of_channels\>), for example: uchar \~ CV_8UC1, 3-element
floating-point tuple \~ CV_32FC3, and so on. A universal OpenCV structure that is able to store a
single instance of such a primitive data type is Vec. Multiple instances of such a type can be
stored in a std::vector, Mat, Mat_, SparseMat, SparseMat_, or any other container that is able to
store Vec instances.

The DataType class is basically used to provide a description of such primitive data types without
adding any fields or methods to the corresponding classes (and it is actually impossible to add
anything to primitive C/C++ data types). This technique is known in C++ as class traits. It is not
DataType itself that is used but its specialized versions, such as:
@code
    template<> class DataType<uchar>
    {
        typedef uchar value_type;
        typedef int work_type;
        typedef uchar channel_type;
        enum { channel_type = CV_8U, channels = 1, fmt='u', type = CV_8U };
    };
    ...
    template<typename _Tp> DataType<std::complex<_Tp> >
    {
        typedef std::complex<_Tp> value_type;
        typedef std::complex<_Tp> work_type;
        typedef _Tp channel_type;
        // DataDepth is another helper trait class
        enum { depth = DataDepth<_Tp>::value, channels=2,
            fmt=(channels-1)*256+DataDepth<_Tp>::fmt,
            type=CV_MAKETYPE(depth, channels) };
    };
    ...
@endcode
The main purpose of this class is to convert compilation-time type information to an
OpenCV-compatible data type identifier, for example:
@code
    // allocates a 30x40 floating-point matrix
    Mat A(30, 40, DataType<float>::type);

    Mat B = Mat_<std::complex<double> >(3, 3);
    // the statement below will print 6, 2 , that is depth == CV_64F, channels == 2
    cout << B.depth() << ", " << B.channels() << endl;
@endcode
So, such traits are used to tell OpenCV which data type you are working with, even if such a type is
not native to OpenCV. For example, the matrix B initialization above is compiled because OpenCV
defines the proper specialized template class DataType\<complex\<_Tp\> \> . This mechanism is also
useful (and used in OpenCV this way) for generic algorithms implementations.

@note Default values were dropped to stop confusing developers about using of unsupported types (see #7599)
*/
template<typename _Tp> class DataType
{
public:
#ifdef OPENCV_TRAITS_ENABLE_DEPRECATED
    typedef _Tp         value_type;
    typedef value_type  work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 1,
           depth        = -1,
           channels     = 1,
           fmt          = 0,
           type = CV_MAKETYPE(depth, channels)
         };
#endif
};

template<> class DataType<bool>
{
public:
    typedef bool        value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_8U,
           channels     = 1,
           fmt          = (int)'u',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<uchar>
{
public:
    typedef uchar       value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_8U,
           channels     = 1,
           fmt          = (int)'u',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<schar>
{
public:
    typedef schar       value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_8S,
           channels     = 1,
           fmt          = (int)'c',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<char>
{
public:
    typedef schar       value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_8S,
           channels     = 1,
           fmt          = (int)'c',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<ushort>
{
public:
    typedef ushort      value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_16U,
           channels     = 1,
           fmt          = (int)'w',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<short>
{
public:
    typedef short       value_type;
    typedef int         work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_16S,
           channels     = 1,
           fmt          = (int)'s',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<int>
{
public:
    typedef int         value_type;
    typedef value_type  work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_32S,
           channels     = 1,
           fmt          = (int)'i',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<float>
{
public:
    typedef float       value_type;
    typedef value_type  work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_32F,
           channels     = 1,
           fmt          = (int)'f',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<double>
{
public:
    typedef double      value_type;
    typedef value_type  work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_64F,
           channels     = 1,
           fmt          = (int)'d',
           type         = CV_MAKETYPE(depth, channels)
         };
};

template<> class DataType<hfloat>
{
public:
    typedef hfloat   value_type;
    typedef float       work_type;
    typedef value_type  channel_type;
    typedef value_type  vec_type;
    enum { generic_type = 0,
           depth        = CV_16F,
           channels     = 1,
           fmt          = (int)'h',
           type         = CV_MAKETYPE(depth, channels)
         };
};

/** @brief A helper class for cv::DataType

The class is specialized for each fundamental numerical data type supported by OpenCV. It provides
DataDepth<T>::value constant.
*/
template<typename _Tp> class DataDepth
{
public:
    enum
    {
        value = DataType<_Tp>::depth,
        fmt   = DataType<_Tp>::fmt
    };
};


#ifdef OPENCV_TRAITS_ENABLE_DEPRECATED

template<int _depth> class TypeDepth
{
#ifdef OPENCV_TRAITS_ENABLE_LEGACY_DEFAULTS
    enum { depth = CV_USRTYPE1 };
    typedef void value_type;
#endif
};

template<> class TypeDepth<CV_8U>
{
    enum { depth = CV_8U };
    typedef uchar value_type;
};

template<> class TypeDepth<CV_8S>
{
    enum { depth = CV_8S };
    typedef schar value_type;
};

template<> class TypeDepth<CV_16U>
{
    enum { depth = CV_16U };
    typedef ushort value_type;
};

template<> class TypeDepth<CV_16S>
{
    enum { depth = CV_16S };
    typedef short value_type;
};

template<> class TypeDepth<CV_32S>
{
    enum { depth = CV_32S };
    typedef int value_type;
};

template<> class TypeDepth<CV_32F>
{
    enum { depth = CV_32F };
    typedef float value_type;
};

template<> class TypeDepth<CV_64F>
{
    enum { depth = CV_64F };
    typedef double value_type;
};

template<> class TypeDepth<CV_16F>
{
    enum { depth = CV_16F };
    typedef hfloat value_type;
};

#endif

//! @}

namespace traits {

namespace internal {
#define CV_CREATE_MEMBER_CHECK(X) \
template<typename T> class CheckMember_##X { \
    struct Fallback { int X; }; \
    struct Derived : T, Fallback { }; \
    template<typename U, U> struct Check; \
    typedef char CV_NO[1]; \
    typedef char CV_YES[2]; \
    template<typename U> static CV_NO & func(Check<int Fallback::*, &U::X> *); \
    template<typename U> static CV_YES & func(...); \
public: \
    typedef CheckMember_##X type; \
    enum { value = sizeof(func<Derived>(0)) == sizeof(CV_YES) }; \
};

CV_CREATE_MEMBER_CHECK(fmt)
CV_CREATE_MEMBER_CHECK(type)

} // namespace internal


template<typename T>
struct Depth
{ enum { value = DataType<T>::depth }; };

template<typename T>
struct Type
{ enum { value = DataType<T>::type }; };

/** Similar to traits::Type<T> but has value = -1 in case of unknown type (instead of compiler error) */
template<typename T, bool available = internal::CheckMember_type< DataType<T> >::value >
struct SafeType {};

template<typename T>
struct SafeType<T, false>
{ enum { value = -1 }; };

template<typename T>
struct SafeType<T, true>
{ enum { value = Type<T>::value }; };


template<typename T, bool available = internal::CheckMember_fmt< DataType<T> >::value >
struct SafeFmt {};

template<typename T>
struct SafeFmt<T, false>
{ enum { fmt = 0 }; };

template<typename T>
struct SafeFmt<T, true>
{ enum { fmt = DataType<T>::fmt }; };


} // namespace

} // cv

#endif // OPENCV_CORE_TRAITS_HPP