LinearMapper.h

// Linear Mapper set of functions 
// Written by Sergey G. Kosov in 2015 - 2016 for Project X
#pragma once

#include "types.h"
#include "macroses.h"

namespace DirectGraphicalModels { namespace fex
{
    template <typename T>
    inline T linear_mapper(float val, float min, float max)
    {
        DGM_ASSERT(max > min);
        float tMin = static_cast<float>(std::numeric_limits<T>::min());
        float tMax = static_cast<float>(std::numeric_limits<T>::max());
        float a = (tMax - tMin) / (max - min);
        float b = tMin - a * min;
        float x = a * val + b;
        return static_cast<T>(MAX(tMin, MIN(tMax, std::round(x))));
    }
    
    template<typename T>
    inline T two_linear_mapper(float val, float min, float max, float mid, T midPoint)
    {
        if ((mid == min) || (mid == max)) return linear_mapper<T>(val, min, max);
        DGM_ASSERT(max > mid);
        DGM_ASSERT(mid > min);
        float tMin = static_cast<float>(std::numeric_limits<T>::min());
        float tMid = static_cast<float>(midPoint);
        float tMax = static_cast<float>(std::numeric_limits<T>::max());

        float a, b;
        if (val < mid) {
            a = (tMid - tMin) / (mid - min);
            b = tMin - a * min;
        }
        else {
            a = (tMax - tMid) / (max - mid);
            b = tMid - a * mid;
        }

        float x = a * val + b;
        return static_cast<T>(MAX(tMin, MIN(tMax, std::round(x))));
    }

} }