function [len_M, num_false] = add_dataset2(image_file, csv_file, dataset_folder, map_file)

% parameters

% num_false = 26685;

num_false = 26602;

d = 10;

d2 = d*d;

N = 101; % must be odd

R = (N-1)/2;

% load image and csv files

A = imread(image_file);

M = csvread(csv_file);

map = imread(map_file);

[A_height, A_width, ~] = size(A);

% find the centroids

len_M = size(M,1);

P = zeros(len_M,2);

for i=1:len_M;

    tmp = M(i,:);

    tmp = tmp(tmp~=0);

    len_tmp = size(tmp,2);

    sum_X = 0;

    sum_Y = 0;

    for j=1:len_tmp/2

        sum_X = sum_X + tmp(2*j-1);

        sum_Y = sum_Y + tmp(2*j);

    end

    mean_X = 2*sum_X/len_tmp;

    mean_Y = 2*sum_Y/len_tmp;

    P(i,:) = [mean_Y mean_X];

end

M = round(P);

% create negative dataset

H = A_height - N + 1;

W = A_width - N + 1;

B = cell(1,num_false);

for i=1:num_false

    flag = true;

    while flag

        X = randi(W) + R;

        Y = randi(H) + R;

        if randi([0,255]) < map(Y,X)

            flag = isPos(X,Y,M,d);

        end

    end

    y1 = Y - R;

    y2 = Y + R;

    x1 = X - R;

    x2 = X + R;

    B{i} = A(y1:y2, x1:x2, :);

end

% write set of images to file

n = length(dir([dataset_folder '*.png']));

for i=1:num_false

    file = [dataset_folder num2str(i+n,'%02u') '.png'];

    imwrite(B{i}, file, 'png');

end