Convert a JPanel to an image in a JScrollPane

I want to convert an JPanel to an image. I used the following method:

public BufferedImage createImage(){

    int w = getWidth();
    int h = getHeight();
    BufferedImage bi = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);
    Graphics2D g = bi.createGraphics();
    paint(g);
    return bi;
}

But the problem is that the JPanel is contained within a JScrollPane. So when I convert the jpanel to an image, the image contains only the parts visible in the jpanel and the parts that are hidden inside the scrollpane aren't contained in the image.

Are there any solutions to get the full content of the JPanel into an image?

回答1:

But the problem is that the JPanel is contained within a JScrollPane. So when I convert the jpanel to an image, the image contains only the parts visible in the jpanel and the parts that are hidden inside the scrollpane aren't contained in the image.

This doesnt happen to me... have you tried paintAll instead of paint?

Here is a great method which will capture the content of any Component visible or not (Its not mine I got it somewhere off the SO and have used it since):

public static BufferedImage componentToImage(Component component, boolean visible) {
    if (visible) {
        BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TRANSLUCENT);
        Graphics2D g2d = (Graphics2D) img.getGraphics();
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        component.paintAll(g2d);
        return img;
    } else {
        component.setSize(component.getPreferredSize());
        layoutComponent(component);
        BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TRANSLUCENT);
        CellRendererPane crp = new CellRendererPane();
        crp.add(component);
        crp.paintComponent(img.createGraphics(), component, crp, component.getBounds());
        return img;
    }
}

private static void layoutComponent(Component c) {
    synchronized (c.getTreeLock()) {
        c.doLayout();
        if (c instanceof Container) {
            for (Component child : ((Container) c).getComponents()) {
                layoutComponent(child);
            }
        }
    }
}

Here is an example showcasing the above:

The frame view:

capture of the panel:

import java.awt.Component;
import java.awt.Container;
import java.awt.Dimension;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.Image;
import java.awt.RenderingHints;
import java.awt.image.BufferedImage;
import java.io.File;
import java.io.IOException;
import java.net.URL;
import javax.imageio.ImageIO;
import javax.swing.CellRendererPane;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JScrollPane;
import javax.swing.SwingUtilities;

public class Test {

    public Test() {
        createAndShowGui();
    }

    private void createAndShowGui() {
        JFrame frame = new JFrame() {
            @Override
            public Dimension getPreferredSize() {//size frame purposefully smaller
                return new Dimension(100, 100);
            }
        };
        frame.setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

        Image img = null;
        try {
            img = ImageIO.read(new URL("http://images4.wikia.nocookie.net/__cb20120515073660/naruto/images/0/09/Naruto_newshot.png")).getScaledInstance(200, 200, Image.SCALE_SMOOTH);
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        final ImagePanel imagePanel = new ImagePanel(200, 200, img);
        JScrollPane jsp = new JScrollPane(imagePanel);
        frame.add(jsp);


        frame.pack();
        frame.setVisible(true);
        BufferedImage bi = componentToImage(imagePanel, true);
        try {
            File outputfile = new File("c:/saved.png");
            ImageIO.write(bi, "png", outputfile);
        } catch (IOException e) {
            e.printStackTrace();
        }

    }

    public static BufferedImage componentToImage(Component component, boolean visible) {
        if (visible) {
            BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TRANSLUCENT);
            Graphics2D g2d = (Graphics2D) img.getGraphics();
            g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
            component.paintAll(g2d);
            return img;
        } else {
            component.setSize(component.getPreferredSize());
            layoutComponent(component);
            BufferedImage img = new BufferedImage(component.getWidth(), component.getHeight(), BufferedImage.TRANSLUCENT);
            CellRendererPane crp = new CellRendererPane();
            crp.add(component);
            crp.paintComponent(img.createGraphics(), component, crp, component.getBounds());
            return img;
        }
    }

    private static void layoutComponent(Component c) {
        synchronized (c.getTreeLock()) {
            c.doLayout();
            if (c instanceof Container) {
                for (Component child : ((Container) c).getComponents()) {
                    layoutComponent(child);
                }
            }
        }
    }

    public static void main(String[] args) {
        SwingUtilities.invokeLater(new Runnable() {
            @Override
            public void run() {
                new Test();
            }
        });
    }
}

class ImagePanel extends JPanel {

    int width, height;
    Image bg;

    public ImagePanel(int width, int height, Image bg) {
        this.width = width;
        this.height = height;
        this.bg = bg;
    }

    @Override
    public Dimension getPreferredSize() {
        return new Dimension(width, height);
    }

    @Override
    protected void paintComponent(Graphics grphcs) {
        super.paintComponent(grphcs);
        grphcs.drawImage(bg, 0, 0, null);
    }
}

UPDATE:

As per your comment:

I wrote the BufferedImage into a file by using ImageIO.write(bufferedImage, "jpg" , file); this works fine for both png and gif images, but jpg image shows a red background instead of white. How can i slove that problem. Thanks

See this similar question/answer for more. You would do something like:

private static final int[] RGB_MASKS = {0xFF0000, 0xFF00, 0xFF};
private static final ColorModel RGB_OPAQUE = new DirectColorModel(32, RGB_MASKS[0], RGB_MASKS[1], RGB_MASKS[2]);
...

BufferedImage image = componentToImage(imagePanel, true);
saveJPeg(image, "c:/saved.jpg");

private void saveJPeg(BufferedImage image, String name) {
    PixelGrabber pg = new PixelGrabber(image, 0, 0, -1, -1, true);
    try {
        pg.grabPixels();
    } catch (InterruptedException ex) {
        ex.printStackTrace();
    }
    int width = pg.getWidth(), height = pg.getHeight();

    DataBuffer buffer = new DataBufferInt((int[]) pg.getPixels(), pg.getWidth() * pg.getHeight());
    WritableRaster raster = Raster.createPackedRaster(buffer, width, height, width, RGB_MASKS, null);
    BufferedImage bi = new BufferedImage(RGB_OPAQUE, raster, false, null);

    try {
        ImageIO.write(bi, "jpg", new File(name));
    } catch (IOException ex) {
        ex.printStackTrace();
    }
}

回答2:

SwingUtilities.paintComponent does it:

static void drawComponent(JComponent c,
                          BufferedImage destination) {

    JFrame frame = new JFrame();

    Graphics g = destination.createGraphics();

    SwingUtilities.paintComponent(g, c, frame.getContentPane(),
        0, 0, destination.getWidth(), destination.getHeight());

    g.dispose();

    frame.dispose();
}

static BufferedImage createSnapshotOf(JComponent c) {

    Dimension size = c.getSize();
    if (size.width <= 0 || size.height <= 0) {
        size = c.getPreferredSize();
    }

    BufferedImage snapshot =
        new BufferedImage(size.width, size.height,
            BufferedImage.TYPE_INT_ARGB);

    drawComponent(c, snapshot);

    return snapshot;
}

回答3:

I don't know why you need to do something so complicated. As long as your Buffered image and paint function all use the component (huge) that is the in the JScroolPane, the whole thing should be saved.

    //create a tree data structure
    DefaultMutableTreeNode tree = new DefaultMutableTreeNode("root");
    //optional: you can make the tree really big

    //now show the tree
    JFrame frame = new JFrame("TreeDemo");
    frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

    //Create a Jtree component to display your data structure 
    JTree treeDisplay = new JTree(tree);

    //expand the tree all out
    for(int i = 0; i < treeDisplay.getRowCount(); i++) {
        treeDisplay.expandRow(i);
    }

    //put your tree display component in a scroll pane
    frame.add(new JScrollPane(treeDisplay));

    //Display the window.
    frame.pack();
    frame.setVisible(true);

    //save tree in the window to a file
    BufferedImage img = new BufferedImage(treeDisplay.getWidth(), treeDisplay.getHeight(), BufferedImage.TYPE_INT_RGB);
    Graphics2D graphics = img.createGraphics();
    //put graphics on the buffered image
    treeDisplay.paintAll(graphics);    
    graphics.dispose();

    try {
        ImageIO.write(img, "png", new File("tree.png"));
    }
    catch (IOException e) {
        e.printStackTrace();
    }