/homes/esi30/DCS339/coursework/src/Processes/histogram_equalisation.cpp

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#include <algorithm>
#include <memory>
#include <string>

#include <gtkmm/image.h>

#include "../display_unit.hpp"
#include "../processing_page.hpp"
#include "../processing_unit.hpp"
#include "../utils.hpp"
#include "convolution.hpp"

namespace{
    Display_unit* impl(const Image_unit *in){
        std::array<double, 256> red_hist{{}}, green_hist{{}}, blue_hist{{}};

        for(auto pixel: *in){
            red_hist[pixel.r]++;
            green_hist[pixel.g]++;
            blue_hist[pixel.b]++;
        }

        for(unsigned short i=1; i<256; ++i){
            red_hist[i]+=red_hist[i-1];
            green_hist[i]+=green_hist[i-1];
            blue_hist[i]+=blue_hist[i-1];
        }

        for(unsigned short i=1; i<256; ++i){
            red_hist[i]/=static_cast<double>(in->height()*in->width())/255;
            green_hist[i]/=static_cast<double>(in->height()*in->width())/255;
            blue_hist[i]/=static_cast<double>(in->height()*in->width())/255;
        }

        Image_unit *out(new Image_unit(*in));
        for(auto pixel: *out){
            pixel.r=red_hist[pixel.r];
            pixel.g=green_hist[pixel.g];
            pixel.b=blue_hist[pixel.b];
        }

        return out;
    }
}

namespace Processes{
    void histogram_equalisation(){
        Gtk::Image icon(cmake_install_prefix+std::string("/share/egami/icons/histogram_equalisation.png"));
        std::shared_ptr<Processing_unit> pu(new Processing_unit(Processing(&impl), "H. equalisation", icon, false));
        Processing_page::add_unit_to_page("Colours", pu);
    }
}