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# ColorBaseConcept Struct Template Reference
[Concepts]

`#include <gil_concept.hpp>`

List of all members.

## Detailed Description

### template<typename ColorBase>
struct boost::gil::ColorBaseConcept< ColorBase >

A color base is a container of color elements (such as channels, channel references or channel pointers).

COLOR BASE CONCEPTS The most common use of color base is in the implementation of a pixel, in which case the color elements are channel values. The color base concept, however, can be used in other scenarios. For example, a planar pixel has channels that are not contiguous in memory. Its reference is a proxy class that uses a color base whose elements are channel references. Its iterator uses a color base whose elements are channel iterators.

A color base must have an associated layout (which consists of a color space, as well as an ordering of the channels). There are two ways to index the elements of a color base: A physical index corresponds to the way they are ordered in memory, and a semantic index corresponds to the way the elements are ordered in their color space. For example, in the RGB color space the elements are ordered as {red_t, green_t, blue_t}. For a color base with a BGR layout, the first element in physical ordering is the blue element, whereas the first semantic element is the red one. Models of `ColorBaseConcept` are required to provide the `at_c<K>(ColorBase)` function, which allows for accessing the elements based on their physical order. GIL provides a `semantic_at_c<K>(ColorBase)` function (described later) which can operate on any model of ColorBaseConcept and returns the corresponding semantic element.

    concept ColorBaseConcept<typename T> : CopyConstructible<T>, EqualityComparable<T> {
        // a GIL layout (the color space and element permutation)
        typename layout_t;

        // The type of K-th element
        template <int K> struct kth_element_type;                 where Metafunction<kth_element_type>;

        // The result of at_c
        template <int K> struct kth_element_const_reference_type; where Metafunction<kth_element_const_reference_type>;

        template <int K> kth_element_const_reference_type<T,K>::type at_c(T);

        // Copy-constructible and equality comparable with other compatible color bases
        template <ColorBaseConcept T2> where { ColorBasesCompatibleConcept<T,T2> }
            T::T(T2);
        template <ColorBaseConcept T2> where { ColorBasesCompatibleConcept<T,T2> }
            bool operator==(const T&, const T2&);
        template <ColorBaseConcept T2> where { ColorBasesCompatibleConcept<T,T2> }
            bool operator!=(const T&, const T2&);

    };

## Public Member Functions

void | constraints ()

## Public Attributes

ColorBase | cb

The documentation for this struct was generated from the following file:

- gil_concept.hpp