Palette.hh

#ifndef VTESTBED_GRAPHICS_PALETTE_HH
#define VTESTBED_GRAPHICS_PALETTE_HH

#include <blitz/array.h>

namespace vtb {

    namespace graphics {

        template <class T>
        class Palette3 {

        public:
            using color_type = blitz::TinyVector<T,3>;

        private:
            color_type _colors[3];

        public:
            template <class ... Color>
            inline explicit
            Palette3(const Color& ... colors): _colors{colors...} {
                static_assert(sizeof...(colors) == 3, "bad no. of colors");
            }

            inline color_type operator()(T value) const {
                value = blitz::clamp(value, T{-1}, T{1});
                const auto* colors = this->_colors;
                color_type color;
                if (value < 0) { color = colors[0] + (colors[1]-colors[0])*(value+1); }
                else { color = colors[1] + (colors[2]-colors[1])*value; }
                return color;
            }

        };

        template <class T> Palette3<T>
        temperaturePalette() {
            using color_type = typename Palette3<T>::color_type;
            return Palette3<T>{
                color_type{0,0,T{0.878}},
                color_type{1,1,T{0.878}},
                color_type{T{0.878},0,0}
            };
        }

    }

}

#endif // vim:filetype=cpp