How to output the content of a Scenegraph in JavaF

问题:

How to output the content of a Scene graph in JavaFX 2 to an Image. Actually, I am working on an app, which basically designs cards. So, the user just clicks to the various options to customize the scene. Finally I would like to export the scene content to an Image file. How do I do that ?

回答1:

In FX 2.2 new snapshot feature appeared for that matter. You can just say

WritableImage snapshot = scene.snapshot(null);

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With older FX you can use AWT Robot. This is not very good approach as it requires whole AWT stack to start.

            // getting screen coordinates of a node (or whole scene)
            Bounds b = node.getBoundsInParent(); 
            int x = (int)Math.round(primaryStage.getX() + scene.getX() + b.getMinX());
            int y = (int)Math.round(primaryStage.getY() + scene.getY() + b.getMinY());
            int w = (int)Math.round(b.getWidth());
            int h = (int)Math.round(b.getHeight());
            // using ATW robot to get image
            java.awt.Robot robot = new java.awt.Robot();
            java.awt.image.BufferedImage bi = robot.createScreenCapture(new java.awt.Rectangle(x, y, w, h));
            // convert BufferedImage to javafx.scene.image.Image
            java.io.ByteArrayOutputStream stream = new java.io.ByteArrayOutputStream();
            // or you can write directly to file instead
            ImageIO.write(bi, "png", stream);
            Image image = new Image(new java.io.ByteArrayInputStream(stream.toByteArray()), w, h, true, true);

回答2:

Update

JavaFX 2.2 (jdk7u6) added a Node snapshot to image feature which would be the preferred way of accomplishing this task.

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Prior to 2.2, JavaFX currently does not have a public function to convert a Node or Scene to an Image. There is an open feature request for this http://javafx-jira.kenai.com/browse/RT-13751 (anybody can sign up to view the current feature request status).

As a workaround in the meantime, you could use Swing/AWT functions to convert the JavaFX scene to an image and write the resultant image to a file:

BufferedImage img = new Robot().createScreenCapture(
  new java.awt.Rectangle(
    (int)sceneRect.getX(),       (int)sceneRect.getY(),
    (int)sceneRect.getWidth()-1, (int)sceneRect.getHeight()-1));
File file = File.createTempFile("card", ".jpg");
ImageIO.write(img, "jpg", file);

The above code is paraphrased from: JavaFXDev: Screen capture tool.

The sceneRect can be determined by:

Stage stage = (Stage) scene.getWindow();
stage.toFront();
Rectangle sceneRect = new Rectangle(
  stage.getX() + scene.getX(), stage.getY() + scene.getY(), 
  scene.getWidth(), scene.getHeight());

If you follow the above idiom, be careful of threading - such that code accessing the live JavaFX scene only runs on the JavaFX Application Thread and the AWT code only runs on the AWT thread.