Histogram

public class FXMLDocumentController implements Initializable {

    @FXML
    private Pane pane;
    @FXML
    private ImageView imageView;
    private LineChart<Integer, Double> lineChart;
    private ObservableList<XYChart.Series<Integer, Double>> series;

    private Image image;
    @FXML
    private BorderPane borderPane;
    @FXML
    private FlowPane flowPane;

    private final Axis xAxis = new NumberAxis(0, 255, 64);
    private final Axis yAxis = new NumberAxis(0, 100, 10);
    @FXML
    private StackPane leftPane;


    @Override
    public void initialize(URL url, ResourceBundle rb) {
      lineChart = new LineChart(xAxis, yAxis);
      borderPane.widthProperty().addListener(listener -> resize());
      borderPane.heightProperty().addListener(listener -> resize());
    }

    @FXML
    private void loadImageBtn(ActionEvent event) {
        FileChooser fc = new FileChooser();
        fc.getExtensionFilters().addAll(new FileChooser.ExtensionFilter("JPG", "*.jpg"),
                new FileChooser.ExtensionFilter("BMP", "*.bmp"));
        File file = fc.showOpenDialog(IPOG_Zkouska_Histogram.stage);

        if (Objects.nonNull(file)) {
            image = new Image(file.toURI().toString());
            if (image != null && !image.isError()) {
                imageView.setImage(image);
                resize();
                obnovHistogram();
            } else {
                Alert alert = new Alert(AlertType.ERROR);
                alert.setContentText("ERROR image");
                alert.setHeaderText(null);
                alert.setTitle("ERROR");

                alert.showAndWait();
            }
        } else {
            Alert alert = new Alert(AlertType.ERROR);
                alert.setContentText("ERROR file");
                alert.setHeaderText(null);
                alert.setTitle("ERROR");

                alert.showAndWait();
        }

    }

    private void resize() {
        double height = borderPane.getHeight()-flowPane.getPrefHeight();
        lineChart.setPrefHeight(height);

        if (image != null) {

            double pomW = leftPane.getWidth()/image.getWidth();
            double pomH = leftPane.getHeight()/image.getHeight();

            double pomF = pomW < pomH ? pomW : pomH;

            imageView.setFitHeight(pomF*image.getHeight());
            imageView.setFitWidth(pomF*image.getWidth());
        }

    }

    private void obnovHistogram() {
        if (series != null) {
            series.clear();
        }


        lineChart = new LineChart(xAxis, yAxis);
        lineChart.setCreateSymbols(false);
        series = lineChart.getData();
        lineChart.setPrefWidth(300);
        lineChart.setPrefHeight(pane.getHeight());

        double red[] = new double[256];
        double green[] = new double[256];
        double blue[] = new double[256];

        Arrays.fill(red, 0);
        Arrays.fill(green, 0);
        Arrays.fill(blue, 0);

        XYChart.Series<Integer, Double> seriesRed = new XYChart.Series<>();
        XYChart.Series<Integer, Double> seriesGreen = new XYChart.Series<>();
        XYChart.Series<Integer, Double> seriesBlue = new XYChart.Series<>();
        ObservableList<XYChart.Data<Integer, Double>> dataRed = seriesRed.getData();
        ObservableList<XYChart.Data<Integer, Double>> dataGreen = seriesGreen.getData();
        ObservableList<XYChart.Data<Integer, Double>> dataBlue = seriesBlue.getData();

        PixelReader pr = image.getPixelReader();

        for (int i = 0; i < image.getWidth(); i++) {
            for (int j = 0; j < image.getHeight(); j++) {
                Color color = pr.getColor(i, j);
                red[to255(color.getRed())]++;
                green[to255(color.getGreen())]++;
                blue[to255(color.getBlue())]++;
            }

        }

        double maxR = 0;
        double maxG = 0;
        double maxB = 0;

        for (int i = 0; i < red.length; i++) {
            maxR = Math.max(maxR, red[i]);
            maxG = Math.max(maxG, green[i]);
            maxB = Math.max(maxB, blue[i]);
        }

        for (int i = 0; i < red.length; i++) {
            dataRed.add(new XYChart.Data<>(i,(red[i]/maxR)*100));
            dataGreen.add(new XYChart.Data<>(i,(green[i]/maxG)*100));
            dataBlue.add(new XYChart.Data<>(i,(blue[i]/maxB)*100));
        }

        series.addAll(seriesRed, seriesBlue, seriesGreen);
        pane.getChildren().add(lineChart);



    }

    private int to255(double i) {
        return (int)(i*255);
    }

}