Algoritmo de Otsu C++ Procesamiento Digital de Imagenes

main.cpp

// Information -> http://www.labbookpages.co.uk/software/imgProc/otsuThreshold.html

#include <cstdlib>
#include <iostream>
#include <stdlib.h>
#include <vector>
#include <algorithm> // std::min_element, std::max_element
#include <math.h>

#define length(x) (sizeof(x)/sizeof(x[0]))

using namespace std;

double histograma[6] = {8,7,2,6,9,4};
double accHistogramaBack[6];
double accHistogramaFore[6];
double weightBack[6];
double weightFore[6];
double meanBack[6];
double meanFore[6];
double varianceBack[6];
double varianceFore[6];
double classVariance[6];
double sizeImage = 36;

// Funcion que calcula el histograma acumulado 
void calculateAccHistograma()
{
    int sumB = 0;
    int sumF = 0;
    
    accHistogramaBack[0] = 0;
    for(int i = 1; i < length(histograma); i++)
    {
        sumB += histograma[i-1];
        accHistogramaBack[i] = sumB;
    }  
    for(int i = length(histograma) - 1; i >= 0 ; i--)
    {
        sumF += histograma[i];
        accHistogramaFore[i] = sumF;
    }
}

// Funcion que calcula el promedio y lo almacena en un array
void calculateWeight()
{
    double sumB = 0;
    double sumF = 0;
    
    weightBack[0] = sumB;
    
    for(int i = 1; i < length(histograma); i++)
    {
        sumB += histograma[i-1] / sizeImage;
        weightBack[i] = sumB;        
    }
    
    for(int i = length(histograma) - 1; i >= 0 ; i--)
    {
        sumF += histograma[i] / sizeImage;
        weightFore[i] = sumF;
    } 
}

// Funcion que calcula la media
void calculateMean()
{
    int sumB = 0;
    int sumF = 0;
    
    meanBack[0] = 0;
    for(int i = 1; i < length(histograma); i++)
    {
        sumB += (i - 1) * histograma[i - 1];
        meanBack[i] = sumB / accHistogramaBack[i];
    }
      
    for(int i = length(histograma) - 1; i >= 0 ; i--)
    {
        sumF += i * histograma[i];
        meanFore[i] = sumF / accHistogramaFore[i];
    }  
}

// Funcion que calcula la varianza
void calculateVariance()
{    
    int countB = 0;
    int countF = length(histograma);    
    double sumB;
    double sumF;
    
    varianceBack[0] = 0;   
    
    for(int i = 1; i < length(histograma); i++)
    {
        sumB = 0;  
        countB = countB + 1;
        
        for(int j = 0; j < countB; j++)
        {
            sumB += pow(j - meanBack[i] , 2) * histograma[j];            
        }
        varianceBack[i] = sumB / accHistogramaBack[i];
    }
    
    for(int i = length(histograma) - 1; i >= 0  ; i--)
    {
        sumF = 0;
        countF = countF - 1;//9-8
                
        for(int j = length(histograma) - 1; j >= countF; j--)
        {
            sumF += pow(j - meanFore[i] , 2) * histograma[j];  
        }
        varianceFore[i] = sumF / accHistogramaFore[i];
       
    }     
}

void calculateClassVariance()
{
    for(int i = 0; i < length(histograma); i++)
    {
        classVariance[i] = (weightBack[i] * varianceBack[i]) + (weightFore[i] * varianceFore[i]);
    }
}

void result()
{
    double minClassVariance;
    double threshold;
    
    calculateAccHistograma();
    calculateWeight();
    calculateMean();
    calculateVariance();
    calculateClassVariance();
    
    cout<<"Background"<<endl;
    for(int i = 0; i < length(histograma); i++)
    {
        cout<<"Weight: "<<weightBack[i]<<" "<<"Mean: "<<meanBack[i]<<" "<<"Variance: "<<varianceBack[i]<<" "<<endl;
    }
    
    cout<<endl;
    
    cout<<"Foreground"<<endl;
    for(int i = 0; i < length(histograma); i++)
    {     
        cout<<"Weight: "<<weightFore[i]<<" "<<"Mean: "<<meanFore[i]<<" "<<"Variance: "<<varianceFore[i]<<" "<<endl;
    }
    
    cout<<endl;
    
    cout<<"Within Class Variance"<<endl;
    for(int i = 0; i < length(histograma); i++)
    {     
        cout<<classVariance[i]<<endl;
    }
    
    // hallar la varianza minima
    minClassVariance = *std::min_element(classVariance,classVariance+length(classVariance));
    
    // Hallar el indice de la varianza minima, para poder asociarlos con el pixel que seria el threshold
    for(int i = 0; i < length(classVariance); i++)
    {
        if(classVariance[i] == minClassVariance)threshold = i;
    }
    
    cout<<endl<<"Min Class Variance: "<<minClassVariance<<endl<<"Threshold: "<<threshold<<endl;
    
}

int main(int argc, char** argv) {

    result();
    return 0;
}