java - 将 JPanel 转换为 JScrollPane 中的图像

Question

我想将 JPanel 转换为图像。我使用了以下方法:

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;
}

但问题是 JPanel 包含在 JScrollPane 中。因此，当我将 jpanel 转换为图像时，图像仅包含 jpanel 中可见的部分，而隐藏在滚动 Pane 内的部分不包含在图像中。

是否有任何解决方案可以将 JPanel 的全部内容放入图像中？

Answer 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.

这不会发生在我身上......你试过 paintAll 而不是 paint 吗？

这是一个很棒的方法，可以捕获任何可见或不可见的 Component 的内容(这不是我的，我从 SO 的某个地方得到它并从那以后一直使用它):

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);
            }
        }
    }
}

这是一个展示上述内容的例子:

框架 View :

面板捕获:

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);
    }
}

更新:

根据您的评论:

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

参见 this类似的问题/答案更多。你会做这样的事情:

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();
    }
}