JavaFX 2.0+ WebView / WebEngine将网页呈现给图像

Question

I'm looking for a way to load up a page and save the rendering as an image just as you would do with CutyCapt (QT + webkit EXE to do just that).

At the moment and without JavaFX, I do it by calling an external process from java and rendering to file than loading that file into an ImageBuffer... Neither very optimized nor practical and even less cross platform...

Using JavaFX2+ I tried playing with the WebView & WebEngine:

public class WebComponentTrial extends Application {
    private Scene scene;

    @Override
    public void start(final Stage primaryStage) throws Exception {
        primaryStage.setTitle("Web View");
        final Browser browser = new Browser();
        scene = new Scene(browser, 1180, 800, Color.web("#666970"));
        primaryStage.setScene(scene);
        scene.getStylesheets().add("webviewsample/BrowserToolbar.css");
        primaryStage.show();
    }

    public static void main(final String[] args) {
        launch(args);
    }
}
class Browser extends Region {
    static { // use system proxy settings when standalone application
    // System.setProperty("java.net.useSystemProxies", "true");
    }

    final WebView browser = new WebView();
    final WebEngine webEngine = browser.getEngine();

    public Browser() {
        getStyleClass().add("browser");
        webEngine.load("http://www.google.com/");
        getChildren().add(browser);
    }

    @Override
    protected void layoutChildren() {
        final double w = getWidth();
        final double h = getHeight();
        layoutInArea(browser, 0, 0, w, h, 0, HPos.CENTER, VPos.CENTER);
    }

    @Override
    protected double computePrefWidth(final double height) {
        return 800;
    }

    @Override
    protected double computePrefHeight(final double width) {
        return 600;
    }
}

There is a deprecated method : renderToImage in Scene (see links below) that would do something that comes close and with which I'd might be able to work but it is deprecated... It being deprecated in JavaFX seems to mean that there is no javadoc advertising the replacement method and because I don't have access to the code, I cannot see how it was done...

Here are a couple of sites where I found some information but nothing to render a webpage to an image:

http://tornorbye.blogspot.com/2010/02/how-to-render-javafx-node-into-image.html

canvasImage and saveImage(canvasImage, fc.getSelectedFile()) from this one :

http://javafx.com/samples/EffectsPlayground/src/Main.fx.html

Others:

http://download.oracle.com/javafx/2.0/webview/jfxpub-webview.htm
http://download.oracle.com/javafx/2.0/get_started/jfxpub-get_started.htm
http://fxexperience.com/2011/05/maps-in-javafx-2-0/

Answer 1

I have done this by launching JavaFX WebView on a Swing JFrame and JFXPanel. And then I use the paint() method on JFXPanel once the WebEngine status is SUCCEEDED.

You may follow this tutorial to make a WebView: Integrating JavaFX into Swing Applications

The code below demonstrate how I capture the rendered screen from JFXPanel.

public static void main(String args[]) {
    jFrame = new JFrame("Demo Browser");
    jfxPanel = new JFXPanel();
    jFrame.add(jfxPanel);
    jFrame.setVisible(true);
    jFrame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    SwingUtilities.invokeLater(new Runnable() {
        @Override
        public void run() {
            Platform.runLater(new Runnable() {
                @Override
                public void run() {
                    browser = new FXBrowser();
                    jfxPanel.setScene(browser.getScene());
                    jFrame.setSize((int) browser.getWebView().getWidth(), (int) browser.getWebView().getHeight());

                    browser.getWebEngine().getLoadWorker().stateProperty().addListener(
                            new ChangeListener() {
                                @Override
                                public void changed(ObservableValue observable,
                                                    Object oldValue, Object newValue) {
                                    State oldState = (State) oldValue;
                                    State newState = (State) newValue;
                                    if (State.SUCCEEDED == newValue) {
                                        captureView();
                                    }
                                }
                            });
                }
            });
        }
    });
}

private static void captureView() {
    BufferedImage bi = new BufferedImage(jfxPanel.getWidth(), jfxPanel.getHeight(), BufferedImage.TYPE_INT_ARGB);
    Graphics graphics = bi.createGraphics();
    jfxPanel.paint(graphics);
    try {
        ImageIO.write(bi, "PNG", new File("demo.png"));
    } catch (IOException e) {
        e.printStackTrace();
    }
    graphics.dispose();
    bi.flush();
}

Answer 2

For JavaFX 2.2 users there is a much more clean and elegant solution based on JavaFX Node snapshot. You can take a look to JavaFX node documentation at:

http://docs.oracle.com/javafx/2/api/javafx/scene/Node.html

Here is an example of taking a capture from a WebView Node (as webView)

   File destFile = new File("test.png");
   WritableImage snapshot = webView.snapshot(new SnapshotParameters(), null);
   RenderedImage renderedImage = SwingFXUtils.fromFXImage(snapshot, null);
   try {
       ImageIO.write(renderedImage, "png", destFile);
   } catch (IOException ex) {
       Logger.getLogger(GoogleMap.class.getName()).log(Level.SEVERE, null, ex);
   }

I had no problems with this solution, and the webview is rendered perfectly in the PNG according to the node size. Any JavaFx node can be rendered and saved to a file with this method.

Hope this help!

Answer 3

Workaround posted by JavaFX engineers: Snapshot does not work with (invisible) WebView nodes .

When taking a snapshot of a scene that contains a WebView node, wait for at least 2 frames before issuing the snapshot command. This can be done by using a counter in an AnimationTimer to skip 2 pulses and take the snapshot on the 3rd pulse.

Once you have got your snapshot, you can convert the image to an awt BufferedImage and encode the image to format like png or jpg, using ImageIO .