private BufferedImage NiblackAlgorithm(BufferedImage image) {
        if (image != null) {
            int windowSize = Integer.parseInt(windowSizeField.getText());
            double k = Double.parseDouble(niblackParamField.getText());
            System.out.println("" + windowSize + " " + k);
            if (windowSize % 2 == 1) {
                for (int i = windowSize / 2; i < image.getWidth() - windowSize / 2; ++i) {
                    for (int j = windowSize / 2; j < image.getHeight() - windowSize / 2; ++j) {

                        int[] h = new int[256];
                        int[] blok = new int[windowSize * windowSize];
                        for (int m = 0; m < windowSize; ++m) {
                            for (int n = 0; n < windowSize; ++n) {
                                Color c = new Color(image.getRGB(i - windowSize / 2 + m, j - windowSize / 2 + n));
                                blok[m * windowSize + n] = c.getRed();
                                h[c.getRed()]++;
                            }
                        }
                        double mean = meanPix(0, 255, h);
                        double sum = sumPix(0, 255, h);

                        double var = 0;

                        for (int T = 0; T < 255; T++) {

                            var += (T - mean) * (T - mean) * h[T];

                        }
                        var /= sum;

                        double threshold = mean + k * Math.sqrt(var);
                        Color c = new Color(image.getRGB(i, j));
                        image.setRGB(i, j, c.getRed() > threshold ? Color.WHITE.getRGB() : Color.BLACK.getRGB());
                    }
                }
            }

        }
        return image;
    }