void calculate_adjacency() {

    //Sorting the vector from smallest to biggest
    sort(regions.begin(), regions.end(), [](const Region& r1, const Region& r2) { return r1.pixel_num < r2.pixel_num; });

    //aux tmp regions variables
    Region analyzed, extracted;

    //for the entire regions vector, extracting the current analyzed region
    for(int i=0; i<regions.size(); i++) {

        //analyzed is the region being analyzed to all the other region
        analyzed = regions.at(i);

        //calculate the center of the rect
        int row_cen = round((analyzed.area.height + analyzed.area.y)/2);
        int col_cen = round((analyzed.area.width + analyzed.area.x)/2);
        Point c(col_cen, row_cen);

        //the distance from the center to any of the side
        int distance = (c.y - analyzed.area.y);

        //calculating the middle point +- 2 to get a point into the adjacent regions
        Point N(c.x, (c.y - distance)-2);
        Point E((c.x - distance)-2, c.y);
        Point S(c.x, (c.y + distance)+2);
        Point W((c.x + distance)+2, c.y);

        //analyze all the vector
        for(int j=0; j<regions.size(); j++) {
            if(j==i) continue;

            extracted = regions.at(j);

            //if the size of the region is <= than the extracted region from the list
            if(analyzed.pixel_num <= extracted.pixel_num) {
                //and if the extracted region contains any of the point calculated before
                if(extracted.contains(N) || extracted.contains(S) || extracted.contains(E) || extracted.contains(W)) {
                    //update both of the adjacent set of the region
                    regions.at(i).adjacency.insert(extracted);
                    regions.at(j).adjacency.insert(analyzed);
                }
            }
        }

    }

}