awesome-attractor-nd/AwesomeAttractorND/Tonemapper.hpp

//
//  Tonemapper.hpp
//  AwesomeAttractorND
//
//  Created by Joshua Moerman on 10/28/11.
//  Copyright 2011 Vadovas. All rights reserved.
//

#ifndef AwesomeAttractorND_Tonemapper_hpp
#define AwesomeAttractorND_Tonemapper_hpp

#include <algorithm>
#include <numeric>
#include <cmath>

namespace Tonemappers {
	
	struct Normalizer {
		Normalizer()
		: max(0)
		{}
		
		template <typename C>
		void analyse(C const & canvas){
			max = *std::max_element(canvas.begin(), canvas.end());
		}
		
		template <typename C, typename I>
		void process(C const & canvas, I & image){
			for (typename C::const_iterator it = canvas.begin(); it != canvas.end(); ++it) {
				const double grayscale = get_value(*it);
				image << typename I::pixel(grayscale, grayscale, grayscale);
			}
		}
		
	protected:
		double get_value(unsigned int n){
			return (double) n / (double) max;
		}
		unsigned int max;
	};
	
	struct GammaCorrector : public Normalizer {
		template <typename C>
		void analyse(C const & canvas){
			Normalizer::analyse(canvas);
			const unsigned int sum = std::accumulate(canvas.begin(), canvas.end(), 0);
			const double average = sum / (double) canvas.size();
			power = -2.5/std::log(average/max);
		}
		
		template <typename C, typename I>
		void process(C const & canvas, I & image){
			for (typename C::const_iterator it = canvas.begin(); it != canvas.end(); ++it) {
				const double grayscale = get_value(*it);
				image << typename I::pixel(grayscale, grayscale, grayscale);
			}
		}
		
	protected:
		double get_value(unsigned int n){
			return std::pow(Normalizer::get_value(n), power);
		}
		double power;
	};

}

#endif