8 #ifndef BOOST_GIL_CONCEPTS_FWD_HPP     9 #define BOOST_GIL_CONCEPTS_FWD_HPP    11 namespace boost { 
namespace gil {
    15 template <
typename ColorBase, 
int K> 
struct kth_element_type;
    16 template <
typename ColorBase, 
int K> 
struct kth_element_reference_type;
    17 template <
typename ColorBase, 
int K> 
struct kth_element_const_reference_type;
    18 template <
typename ColorBase, 
int K> 
struct kth_semantic_element_reference_type;
    19 template <
typename ColorBase, 
int K> 
struct kth_semantic_element_const_reference_type;
    20 template <
typename ColorBase> 
struct size;
    21 template <
typename ColorBase> 
struct element_type;
    23 template <
typename T> 
struct is_pixel;
    24 template <
typename T> 
struct is_planar;
    25 template <
typename T> 
struct channel_type;
    26 template <
typename T> 
struct color_space_type;
    27 template <
typename T> 
struct channel_mapping_type;
    28 template <
typename T> 
struct num_channels;
    30 template <
typename T> 
struct dynamic_x_step_type;
    31 template <
typename T> 
struct dynamic_y_step_type;
    32 template <
typename T> 
struct transposed_type;