Source code: CaptureTest

Código fuente del programa CaptureTest

Ver la entrada correspondiente en el siguiente enlace:

Capturar un Component de Swing (renderizar a una imagen)

package pruebas;

import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Component;
import java.awt.Graphics;
import java.awt.Insets;
import java.awt.Window;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.image.BufferedImage;
import java.awt.image.RenderedImage;
import java.io.File;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JOptionPane;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.JTextArea;
import javax.swing.SwingUtilities;

public class CaptureTest {

    public static RenderedImage capture(Component component, Color background) {
        //Se crea una imagen de las dimensiones del componente.
        int width= component.getWidth();
        int height= component.getHeight();

        //El tamaño de las ventanas incluye las decoraciones si las hay, que no se pintan en el método paint(Graphics).
        if (component instanceof Window) {
            Window window= (Window) component;
            Insets insets= window.getInsets();

            if (insets != null) {
                //Hay que restar el ancho y el alto del Insets (Border y decoración).
                width= width - (insets.left + insets.right);
                height= height - (insets.top + insets.bottom);
            }
        }

        int imageType= BufferedImage.TYPE_INT_ARGB;
        BufferedImage bufImage= new BufferedImage(width, height, imageType);

        //Se pinta el componente sobre la imagen creada.
        Graphics graphics= bufImage.getGraphics();

        //El tamaño de las ventanas incluye las decoraciones si las hay, que no se pintan en el método paint(Graphics).
        if (component instanceof Window) {
            Window window= (Window) component;
            Insets insets= window.getInsets();

            if (insets != null) {
                //Hay que mover el origen.
                graphics.translate(
                    0 - insets.left,
                    0 - insets.top
                );
            }
        }

        //Si el componente no es opaco y se ha indicado un color de fondo.
        if (component.isOpaque() == false) {
            if (background != null) {
                graphics.setColor(background);
                graphics.fillRect(0, 0, width, height);
            }
        }

        component.paint(graphics);

        graphics.dispose();

        return bufImage;
    }


    private static File doCapture(Component component, String fileName) {
        try {
            RenderedImage image= CaptureTest.capture(component, null);
            File file= new File(fileName);
            boolean wasOK= ImageIO.write(image, "PNG", file);

            return file;
        }
        catch (IOException ex) {
            ex.printStackTrace(System.err);
            System.exit(1);
            return null;//Necesario para que compile.
        }
    }


    public static void test() {
        final JTextArea ta= new JTextArea();
        ta.setText("This is a very looooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooog line.");
        ta.setCaretPosition(0);

        JScrollPane scroll= new JScrollPane(ta);

        JButton bCaptureTA= new JButton("Capture Text Area");

        JButton bCaptureWin= new JButton("Capture Window");

        JPanel panel= new JPanel( new BorderLayout() );
        panel.add(scroll, BorderLayout.CENTER);
        panel.add(bCaptureTA, BorderLayout.PAGE_START);
        panel.add(bCaptureWin, BorderLayout.PAGE_END);

        final JFrame frame= new JFrame();
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setContentPane(panel);
        frame.setSize(300, 200);

        bCaptureTA.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                File file= CaptureTest.doCapture(ta, "ta.png");
                String msg= String.format("Saved to file <%s>.", file.getAbsolutePath());
                JOptionPane.showMessageDialog(frame, msg);
            }
        });

        bCaptureWin.addActionListener(new ActionListener() {
            @Override
            public void actionPerformed(ActionEvent e) {
                //Se usa invokeLater para que el botón no se capture pulsado.
                SwingUtilities.invokeLater(new Runnable() { public void run() {
                    File file= CaptureTest.doCapture(frame, "win.png");
                    String msg= String.format("Saved to file <%s>.", file.getAbsolutePath());
                    JOptionPane.showMessageDialog(frame, msg);
                }});
            }
        });

        frame.setVisible(true);
    }


    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() { public void run() {
            CaptureTest.test();
        }});
    }

}