问题
I have set up a background Task that waits several seconds after a given Panel/Chart become visible. That is performed by running a sleep
on a background non-GUI thread and then upon waking up it runs a
Platform.runLater
to create the snapshot and image.
Before the real 'action' for saving the image occurs we can see the window come up:
While that image is rendering we have the background code that has been put to sleep by a Task
. After 5000 millis that background task wakes up and launches a Platform.runLater
to save the scene/pane/chart to a file.
Here is the snapshot and image code:
All this happens on a background thread via a Task
submitted to a ThreadPool
Thread.sleep(5000) // Wait for images to be rendered -
// they are visually confirmed to be available at about 1000 ms actually
javafx.application.Platform.runLater(new Runnable() {
override def run() = {
// val snapShot = chart.snapshot(null)
// val snapShot = scene.snapshot(null)
val snapShot = pane.snapshot(null,null)
ImageIO.write(SwingFXUtils.fromFXImage(snapShot, null),
"jpg", new File(fileName))
As you can see (from the commented out lines) - I have confused about which object to use for creating the snapshot: all three above have been attempted:
- Chart
- Scene
- Pane
Always the result is a Black Image. OOC I also tried changing the background color via
snapshotParameters.setFill(Color.WHITE)
That had no effect.
What is the correct procedure ?
Update I also tried a callback
approach:
pane.snapshot( // Also tried scene and chart here ..
new Callback[SnapshotResult, Void]() {
override def call(result: SnapshotResult): Void = {
ImageIO.write(SwingFXUtils.fromFXImage(result.getImage, null),
"jpg", new File(fileName))
latch.countDown
null
}
},p,null)
Likewise - still a Black Image.
回答1:
Using such kinds of heuristics is rather risky. However, you didn't provide a full MCVE. If you want to do it that way, you could use a PauseTransition, snapshot any node and then save the image to a file.
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import javafx.animation.PauseTransition;
import javafx.application.Application;
import javafx.embed.swing.SwingFXUtils;
import javafx.scene.Node;
import javafx.scene.Scene;
import javafx.scene.SnapshotParameters;
import javafx.scene.chart.LineChart;
import javafx.scene.chart.NumberAxis;
import javafx.scene.chart.XYChart;
import javafx.scene.image.Image;
import javafx.scene.image.WritableImage;
import javafx.scene.layout.AnchorPane;
import javafx.scene.paint.Color;
import javafx.stage.Stage;
import javafx.util.Duration;
import javax.imageio.ImageIO;
public class AutoSnapshot extends Application {
private static String fileName = "c:/temp/image.jpg";
private static Color backgroundColor = Color.WHITE;
@Override
public void start(Stage primaryStage) {
AnchorPane root = new AnchorPane();
// dummy chart
final NumberAxis xAxis = new NumberAxis();
final NumberAxis yAxis = new NumberAxis();
xAxis.setLabel("Number of Month");
final LineChart<Number, Number> lineChart = new LineChart<Number, Number>(xAxis, yAxis);
lineChart.setTitle("Stock Monitoring, 2010");
XYChart.Series series = new XYChart.Series();
series.setName("My portfolio");
series.getData().add(new XYChart.Data(1, 23));
series.getData().add(new XYChart.Data(2, 14));
series.getData().add(new XYChart.Data(3, 15));
series.getData().add(new XYChart.Data(4, 24));
lineChart.getData().add(series);
root.getChildren().add( lineChart);
Scene scene = new Scene(root, 800, 600, backgroundColor);
primaryStage.setScene(scene);
primaryStage.show();
Duration delay = Duration.seconds(5);
PauseTransition pt = new PauseTransition(delay);
pt.setOnFinished(e -> {
saveSnapshot(lineChart);
});
pt.play();
}
public static Image createImage(Node node) {
WritableImage wi;
SnapshotParameters parameters = new SnapshotParameters();
parameters.setFill(backgroundColor);
int imageWidth = (int) node.getBoundsInLocal().getWidth();
int imageHeight = (int) node.getBoundsInLocal().getHeight();
wi = new WritableImage(imageWidth, imageHeight);
node.snapshot(parameters, wi);
return wi;
}
private static void saveSnapshot(Node node) {
Image image = createImage(node);
// save image !!! has bug because of transparency (use approach below) !!!
// ImageIO.write(SwingFXUtils.fromFXImage( selectedImage.getImage(), null), "jpg", file);
// save image (without alpha)
BufferedImage bufImageARGB = SwingFXUtils.fromFXImage(image, null);
BufferedImage bufImageRGB = new BufferedImage(bufImageARGB.getWidth(), bufImageARGB.getHeight(), BufferedImage.OPAQUE);
Graphics2D graphics = bufImageRGB.createGraphics();
graphics.drawImage(bufImageARGB, 0, 0, null);
try {
ImageIO.write(bufImageRGB, "jpg", new File(fileName));
} catch (IOException e) {
e.printStackTrace();
}
graphics.dispose();
System.out.println( "Image saved: " + fileName);
}
public static void main(String[] args) {
launch(args);
}
}
回答2:
After all that .. the answer is that "jpg" is simply not working. "png" format works fine.
来源:https://stackoverflow.com/questions/31909297/getting-black-image-when-saving-a-javafx-snapshot