如何将Pane的图像快照保存为BMP？

Question

我已成功在同一窗格上绘制两个图表（条形图和折线图）。

我正在尝试实现一个保存按钮，单击该按钮时，会将生成的图像（带轴）写入我保存的选择的 bmp 图像中。

代码运行，我收到肯定的警报，并创建了一个图像文件。然而，生成的图像文件是空的（0 字节）。

@FXML // fx:id="graph"
    private Pane graph; // Value injected by FXMLLoader

@FXML // fx:id="saveButton"
    private Button saveButton; // Value injected by FXMLLoader

// ...

@FXML
    void clickSave(ActionEvent event) {
        Stage yourStage = (Stage) saveButton.getScene().getWindow();

        FileChooser fileChooser = new FileChooser();
        fileChooser.setInitialDirectory(new File("Path\\With\\Spaces"));
        fileChooser.getExtensionFilters().add(new FileChooser.ExtensionFilter("BMP Files", "*.bmp"));

        // Show save dialog
        File file = fileChooser.showSaveDialog(yourStage);

        if (file != null) {
            if (!file.exists()) {
                try {
                    Files.createFile(file.toPath());
                } catch (IOException e) {
                    e.printStackTrace(); // Handle the exception
                }
            }

            WritableImage writableImage = graph.snapshot(new SnapshotParameters(), null);
            BufferedImage bufferedImage = SwingFXUtils.fromFXImage(writableImage, null);

            try {
                ImageIO.write(bufferedImage, "BMP", file);

                // Inform the user about the successful save
                Alert alert = new Alert(Alert.AlertType.INFORMATION);
                alert.setTitle("File Saved");
                alert.setHeaderText(null);
                alert.setContentText("The file has been saved successfully.");
                alert.showAndWait();
            } catch (IOException e) {
                e.printStackTrace();

                // Inform the user about the error
                Alert alert = new Alert(Alert.AlertType.ERROR);
                alert.setTitle("Error");
                alert.setHeaderText(null);
                alert.setContentText("An error occurred while saving the file.");
                alert.showAndWait();
            }
        }
    }

编辑： 按照@James_D的评论建议，我将代码更改为以下内容，但问题仍然存在。

@FXML
    void clickSave(ActionEvent event) {
        Stage stage = (Stage) saveButton.getScene().getWindow();

        FileChooser fileChooser = new FileChooser();
        fileChooser.setInitialDirectory(new File("Path\\With\\Spaces"));
        fileChooser.getExtensionFilters().add(new FileChooser.ExtensionFilter("BMP Files", "*.bmp"));

        // Show save dialog
        File file = fileChooser.showSaveDialog(stage);

        if (file != null) {
            WritableImage writableImage = graph.snapshot(new SnapshotParameters(), null);
            BufferedImage bufferedImage = SwingFXUtils.fromFXImage(writableImage, null);

            try {
                ImageIO.write(bufferedImage, "BMP", file);

                if (!file.exists()) {
                    Files.createFile(file.toPath());
                }

                // Inform the user about the successful save
                Alert alert = new Alert(Alert.AlertType.INFORMATION);
                alert.setTitle("File Saved");
                alert.setHeaderText(null);
                alert.setContentText("The file has been saved successfully.");
                alert.showAndWait();
            } catch (IOException e) {
                e.printStackTrace();

                // Inform the user about the error
                Alert alert = new Alert(Alert.AlertType.ERROR);
                alert.setTitle("Error");
                alert.setHeaderText(null);
                alert.setContentText("An error occurred while saving the file.");
                alert.showAndWait();
            }
        }
    }

Answer 1

非常感谢@Slaw 和这个答案。

SwingFXUtils 函数返回

TYPE_INT_ARGB_PRE

类型的图像。只有

TYPE_INT_RGB

类型的图像才能写入 .bmp 文件，否则

ImageIO.write(bufferedImage, "BMP", file);

返回

false

。因此，必须进行从

TYPE_INT_ARGB_PRE

到

TYPE_INT_RGB

的适当转换。下面的块显示了更新后的感兴趣的代码，其中现在包括转换。

WritableImage writableImage = graph.snapshot(new SnapshotParameters(), null);
BufferedImage preBufferedImage = SwingFXUtils.fromFXImage(writableImage, null);

BufferedImage bufferedImage = new BufferedImage(
        preBufferedImage.getWidth(),
        preBufferedImage.getHeight(),
        BufferedImage.TYPE_INT_RGB
);
bufferedImage.createGraphics().drawImage(
        preBufferedImage,
        0,
        0,
        java.awt.Color.WHITE,
        null
);

try {
    Boolean __ = ImageIO.write(bufferedImage, "BMP", file);

    if (!file.exists()) {
        Files.createFile(file.toPath());
    }
    ...
}