JavaFX 8 – Mandelbrot stage 2

The source file has grown by some 53 lines so what have we gained:

  • A more colourful palette, the values of which are pre-computed for each possible iteration value:
palette = new int[MAX_ITER];  
for (int i = 0; i<palette.length; i++)  
    palette[i] = java.awt.Color.HSBtoRGB(i/256f, 1, i/(i+8f));
  • The ability to zoom in and out of the set based on mouse location:
imageView.addEventHandler(MouseEvent.MOUSE_CLICKED, (mouseEvent) -> {
    if(mouseEvent.getButton() == javafx.scene.input.MouseButton.PRIMARY) {  
        ZOOM = ZOOM * 0.5;  
    if(mouseEvent.getButton() == javafx.scene.input.MouseButton.SECONDARY) {  
        ZOOM = ZOOM / 0.5;  
    offsetX = offsetX+ ZOOM *(mouseEvent.getX()-(width/2));  
    offsetY = offsetY+ ZOOM *(mouseEvent.getY()-(height/2));
    System.out.printf("offset (x/y): (%f / %f)", offsetX, offsetY);       

  • The method which computes the Mandelbrot set is run in a separate thread to the application. The result of which is then displayed in the imageView:
private void calculate() {
    if (!calculationInProgress.getAndSet(true)) {
        System.out.println("calculate spawned");
        Task calculate = createWorker();

        new Thread(calculate).start();
    } else {
        System.out.println("someone beat us to it!");
private Task createWorker() {
    return new Task() {
        @Override protected Object call() throws Exception {
            Platform.runLater(() -> {
            return true;

What’s left to do?

  • Refine the colour palette used, produce one with more subtle variation.
  • Implement a panning function with the mouse
  • Improve the speed of rendering by using additional threads to produce an inter-laced image.
  • Sort out the ugly pixelation encountered after several zooms

Full source code available here

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