2D kernel support added to numeric extension

Tests for 2D numeric kernel added

include/boost/gil/extension/numeric/kernel.hpp

@@ -151,6 +151,187 @@ inline Kernel reverse_kernel(Kernel const& kernel)
     return result;
 }
 
+
+namespace detail {
+
+template <typename Core>
+class kernel_2d_adaptor : public Core
+{
+public:
+    kernel_2d_adaptor() = default;
+
+    explicit kernel_2d_adaptor(std::size_t center_vertical, std::size_t center_horizontal)
+        : center_vertical_(center_vertical), center_horizontal_(center_horizontal)
+    {
+        BOOST_ASSERT(center_vertical_ < this->size());
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+    }
+
+    kernel_2d_adaptor(std::size_t size, std::size_t center_vertical, std::size_t center_horizontal)
+        : Core(size, typename Core::value_type(size)),
+        center_vertical_(center_vertical),
+        center_horizontal_(center_horizontal)
+    {
+        BOOST_ASSERT(this->size() > 0);
+        BOOST_ASSERT(center_vertical_ < this->size()); // also implies `size() > 0`
+
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        BOOST_ASSERT(this->at(0).size() > 0);
+    }
+
+    kernel_2d_adaptor(kernel_2d_adaptor const& other)
+        : Core(other),
+        center_vertical_(other.center_vertical_),
+        center_horizontal_(other.center_horizontal_)
+    {
+        BOOST_ASSERT(this->size() > 0);
+        BOOST_ASSERT(center_vertical_ < this->size()); // also implies `size() > 0`
+
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        BOOST_ASSERT(this->at(0).size() > 0);
+    }
+
+    kernel_2d_adaptor& operator=(kernel_2d_adaptor const& other)
+    {
+        Core::operator=(other);
+        center_vertical_ = other.center_vertical_;
+        center_horizontal_ = other.center_horizontal_;
+        return *this;
+    }
+
+    std::size_t upper_size() const
+    {
+        BOOST_ASSERT(center_vertical_ < this->size());
+        return center_vertical_;
+    }
+
+    std::size_t lower_size() const
+    {
+        BOOST_ASSERT(center_vertical_ < this->size());
+        return this->size() - center_vertical_ - 1;
+    }
+
+    std::size_t left_size() const
+    {
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        return center_horizontal_;
+    }
+
+    std::size_t right_size() const
+    {
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        return this->at(0).size() - center_horizontal_ - 1;
+    }
+
+    auto center_vertical() -> std::size_t&
+    {
+        BOOST_ASSERT(center_ < this->size());
+        return center_vertical_;
+    }
+
+    auto center_vertical() const -> std::size_t const&
+    {
+        BOOST_ASSERT(center_vertical_ < this->size());
+        return center_vertical_;
+    }
+
+    auto center_horizontal() -> std::size_t&
+    {
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        return center_horizontal_;
+    }
+
+    auto center_horizontal() const -> std::size_t const&
+    {
+        BOOST_ASSERT(center_horizontal_ < this->at(0).size());
+        return center_horizontal_;
+    }
+
+private:
+    std::size_t center_vertical_{ 0 }, center_horizontal_{ 0 };
+};
+} //namespace detail
+
+/// \brief variable-size kernel
+template
+<
+    typename T,
+    typename ColAllocator = std::allocator<T>,
+    typename RowAllocator = std::allocator<std::vector<T, ColAllocator>>
+>
+class kernel_2d :
+    public detail::kernel_2d_adaptor<std::vector<std::vector<T, ColAllocator>, RowAllocator>>
+{
+    using parent_t =
+        detail::kernel_2d_adaptor<std::vector<std::vector<T, ColAllocator>, RowAllocator>>;
+public:
+
+    kernel_2d() = default;
+    kernel_2d(
+        std::size_t size,
+        std::size_t vertical_center,
+        std::size_t center_horizontal
+    ) : parent_t(size, vertical_center, center_horizontal){}
+
+    template <typename FwdIterator>
+    kernel_2d(
+        FwdIterator elements,
+        std::size_t size,
+        std::size_t vertical_center,
+        std::size_t center_horizontal
+    ) : parent_t(size, vertical_center, center_horizontal)
+    {
+        detail::copy_n(elements, size, this->begin());
+    }
+
+    kernel_2d(kernel_2d const& other) : parent_t(other) {}
+    kernel_2d& operator=(kernel_2d const& other) = default;
+};
+
+/// \brief static-size kernel
+template <typename T, std::size_t Size>
+class kernel_2d_fixed :
+    public detail::kernel_2d_adaptor<std::array<std::array<T, Size>, Size>>
+{
+    using parent_t = detail::kernel_2d_adaptor<std::array<std::array<T, Size>, Size>>;
+public:
+    static constexpr std::size_t static_size = Size;
+    static_assert(static_size > 0, "kernel must have size greater than 0");
+    static_assert(static_size % 2 == 1, "kernel size must be odd to ensure validity at the center");
+
+    kernel_2d_fixed() = default;
+    explicit kernel_2d_fixed(std::size_t center_vertical, std::size_t center_horizontal) :
+        parent_t(center_vertical, center_horizontal) {}
+
+    template <typename FwdIterator>
+    explicit kernel_2d_fixed(
+        FwdIterator elements,
+        std::size_t center_vertical,
+        std::size_t center_horizontal
+    ) : parent_t(center_vertical, center_horizontal)
+    {
+        detail::copy_n(elements, Size, this->begin());
+    }
+
+    kernel_2d_fixed(kernel_2d_fixed const& other) : parent_t(other) {}
+    kernel_2d_fixed& operator=(kernel_2d_fixed const& other) = default;
+};
+
+// TODO: This data member is odr-used and definition at namespace scope
+// is required by C++11. Redundant and deprecated in C++17.
+template <typename T, std::size_t Size>
+constexpr std::size_t kernel_2d_fixed<T, Size>::static_size;
+
+/// \brief reverse a kernel
+//template <typename Kernel>
+//inline Kernel reverse_kernel(Kernel const& kernel)
+//{
+//    Kernel result(kernel);
+//    result.center() = kernel.right_size();
+//    std::reverse(result.begin(), result.end());
+//    return result;
+//}
+
 }} // namespace boost::gil
 
 #endif