💿🐜 Antkeeper source code
https://antkeeper.com
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114 lines
2.8 KiB
114 lines
2.8 KiB
/*
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* Copyright (C) 2021 Christopher J. Howard
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*
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* This file is part of Antkeeper source code.
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*
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* Antkeeper source code is free software: you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation, either version 3 of the License, or
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* (at your option) any later version.
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*
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* Antkeeper source code is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with Antkeeper source code. If not, see <http://www.gnu.org/licenses/>.
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*/
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#ifndef ANTKEEPER_PHYSICS_LIGHT_EV_HPP
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#define ANTKEEPER_PHYSICS_LIGHT_EV_HPP
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#include <cmath>
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namespace physics {
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namespace light {
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/**
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* Exposure value.
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*
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* @see https://en.wikipedia.org/wiki/Exposure_value
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*/
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namespace ev {
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/**
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* Exposure value from luminance.
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*
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* @param l Luminance, in cd/m^2.
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* @param s ISO arithmetic speed. A value of `100` corresponds to ISO 100.
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* @param k Reflected-light meter calibration constant. A common value is `12.5`.
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*
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* @return Exposure value.
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*/
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template <class T>
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T from_luminance(T l, T s, T k)
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{
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return std::log2((l * s) / k);
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}
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/**
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* Exposure value from illuminance.
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*
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* @param e Illuminance, in lux.
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* @param s ISO arithmetic speed. A value of `100` corresponds to ISO 100.
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* @param c Incident-light meter calibration constant. A common value is `250`.
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*
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* @return Exposure value.
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*/
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template <class T>
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T from_illuminance(T e, T s, T c)
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{
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return std::log2((e * s) / c);
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}
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/**
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* Exposure value from exposure settings.
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*
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* @param n Relative aperture (f-number).
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* @param t Exposure time (shutter speed), in seconds.
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* @param s ISO arithmetic speed. A value of `100` corresponds to ISO 100.
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*
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* @return Exposure value.
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*/
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template <class T>
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T from_settings(T n, T t, T s)
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{
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return std::log2((n * n) / t * T(100) / s);
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}
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/**
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* Exposure value to luminance.
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*
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* @param ev Exposure value.
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* @param s ISO arithmetic speed. A value of `100` corresponds to ISO 100.
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* @param k Reflected-light meter calibration constant. A common value is `12.5`.
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*
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* @return Luminance, in cd/m^2.
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*/
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template <class T>
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T to_luminance(T ev, T s, T k)
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{
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return (k * std::exp2(ev)) / s;
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}
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/**
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* Exposure value to luminance.
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*
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* @param ev Exposure value.
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* @param s ISO arithmetic speed. A value of `100` corresponds to ISO 100.
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* @param k Incident-light meter calibration constant. A common value is `250`.
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*
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* @return Illuminance, in lux.
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*/
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template <class T>
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T to_luminance(T ev, T s, T c)
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{
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return (c * std::exp2(ev)) / s;
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}
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} // namespace ev
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} // namespace light
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} // namespace physics
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#endif // ANTKEEPER_PHYSICS_LIGHT_EV_HPP
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