java - 保存 JavaFX 快照时获取黑色图像

Question

我设置了一个后台任务，在给定的面板/图表变得可见后等待几秒钟。这是通过在后台非 GUI 线程上运行 sleep 来执行的，然后在唤醒时运行

Platform.runLater

创建快照和图像。

在保存图像的真正“操作”发生之前，我们可以看到窗口出现:

当该图像正在渲染时，我们的后台代码已被任务置于 sleep 状态。 5000 毫秒后，后台任务将唤醒并启动 Platform.runLater 将场景/ Pane /图表保存到文件中。

这是快照和图像代码:

所有这些都通过提交到ThreadPool的Task在后台线程上发生

    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))

正如您所看到的(从注释掉的行中) - 我对使用哪个对象来创建快照感到困惑:以上三个对象都已尝试过:

• 图表
• 场景
• Pane

结果始终是黑色图像。 OOC 我也尝试通过

更改背景颜色

snapshotParameters.setFill(Color.WHITE)

这没有效果。

正确的程序是什么？

更新我还尝试了回调方法:

        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)

同样 - 仍然是黑色图像。

Answer 1

使用这种启发法是相当危险的。但是，您没有提供完整的 MCVE。如果您想这样做，您可以使用 PauseTransition，对任何节点进行快照，然后将图像保存到文件中。

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);
    }
}