如何使用Java中的SVG Salamander库从SVG文件提取单个几何形状

Question

我需要在Java中使用Apache Batik和SVG Salamander库的支持。 我编写了以下示例，该示例在JFrame中展示了一系列几何形状。 随后，使用Apache Batik库，将绘制的内容转换为SVG文件。

public void paint(Graphics g) {
    Graphics2D g2 = (Graphics2D) g;
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, 
            RenderingHints.VALUE_ANTIALIAS_ON);

    g2.setPaint(fg);

    // draw Text
    g2.drawString("Shapes", 250, 400);

    // draw Line2D.Double
    g2.setPaint(orange);
    g2.draw(new Line2D.Double(50, 50, 200, 200));

    // draw Point2D.Double
    g2.setPaint(red);
    g2.fill(new Ellipse2D.Double(400, 400, 5, 5));

    // draw Rectangle2D.Double
    g2.setPaint(magenta);
    g2.draw(new Rectangle2D.Double(600, 600, 300, 150));
    g2.setPaint(magenta);
    g2.draw(new Rectangle2D.Double(300, 300, 300, 150));

    // draw Ellipse2D.Double
    g2.setPaint(blue);
    g2.draw(new Ellipse2D.Double(400, 400, 200, 200));

    // draw GeneralPath (polygon)
    g2.setPaint(green);
    int x1Points[] = {200, 500, 300};
    int y1Points[] = {100, 100, 300};
    GeneralPath polygon = new GeneralPath(GeneralPath.WIND_EVEN_ODD, 
            x1Points.length);
    polygon.moveTo(x1Points[0], y1Points[0]);

    for ( int index = 1; index < x1Points.length; index++ ) {
        polygon.lineTo(x1Points[index], y1Points[index]);
    };

    polygon.closePath();

    g2.draw(polygon);
}

public void loadSVG(String path){

    System.out.println("In loadSVG");
    File file = new File(path);
    SVGUniverse universe = new SVGUniverse();

    URI svgURI = null;      
    try {
        //svgUri = universe.loadSVG(fis, file.toURI().toString());
        svgURI = universe.loadSVG(file.toURL());
    } catch (IOException e) {
        // TODO Auto-generated catch block
        e.printStackTrace();
    }

    SVGPanel svgPanel = new SVGPanel();

    svgPanel.setSvgURI(svgURI);

    SVGDiagram diagram = universe.getDiagram(svgURI);

    SVGRoot root = diagram.getRoot();

    List<Object> l = root.getChildren(null);

    //Create application window/container           
    JFrame frame = new JFrame("Shapes Example From SVG");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    frame.setSize(new Dimension(1000, 1000));
    frame.setLocation(1000, 0);
    frame.add(svgPanel);            
    frame.setResizable(false);
    frame.setVisible(true);      

}

public static void main(String s[]) {
    JFrame f = new JFrame("Shapes Example");
    f.addWindowListener(new WindowAdapter() {
        public void windowClosing(WindowEvent e) {System.exit(0);}
    });

    // Get a DOMImplementation.
    DOMImplementation domImpl = GenericDOMImplementation.getDOMImplementation();

    // Create an instance of org.w3c.dom.Document.
    String svgNS = "http://www.w3.org/2000/svg";
    Document document = domImpl.createDocument(svgNS, "svg", null);

    SVGGeneratorContext ctx = SVGGeneratorContext.createDefault(document);
    ctx.setComment("Generated from ShapesDemo2D");
    ctx.setEmbeddedFontsOn(true);

    // Create an instance of the SVG Generator.
    SVGGraphics2D svgGenerator = new SVGGraphics2D(ctx, false);

    JPanel pane = new ShapesExample();
    f.getContentPane().add("Center", pane);
    f.pack();
    f.setSize(new Dimension(1000,1000));
    f.setResizable(false);
    f.setVisible(true);

    pane.paint(svgGenerator);

    // Finally, stream out SVG to the standard output using
    // UTF-8 encoding.
    boolean useCSS = true; // we want to use CSS style attributes

    String svgFile = "example.svg";

    try {
        OutputStream outputStream = new FileOutputStream(svgFile);
        Writer       outputStreamWriter = new OutputStreamWriter(outputStream);
        svgGenerator.stream(outputStreamWriter, useCSS);
    } catch (Exception e1) {
        // TODO Auto-generated catch block
        e1.printStackTrace();
    }       

    ((ShapesExample)pane).loadSVG(svgFile);
}

在loadSVG（）方法中，我需要在新的JFrame中呈现从SVG文件读取的表单。 如何使用SVG Salamander库从SVG文件中提取单个几何形状，并在Graphics2D“上下文”中报告它们？ 谢谢大家的支持！