Swing：获取JFrame的图像

潘自强

2023-03-14

问题内容：

如何获得java.awt.ImageJFrame的？

我想获取的屏幕截图JFrame（以供以后在我的应用程序中使用）。目前，这是通过使用机器人进行截屏来指定相关对象的坐标和尺寸来完成的JFrame。

但是，我相信有一种更好的方法：默认情况下，Swing组件在将其自身绘制到屏幕上之前，将它们自己作为图像呈现到双缓冲区中。

有没有办法从组件中获取这些图像？

问题答案：

ComponentImageCapture.java

import java.awt.BorderLayout;
import java.awt.Component;
import java.awt.Image;
import java.awt.Graphics;

import java.awt.image.BufferedImage;

import java.awt.event.ActionListener;
import java.awt.event.ActionEvent;
import java.awt.event.KeyEvent;
import java.awt.event.InputEvent;

import javax.swing.*;

import javax.swing.border.TitledBorder;

import javax.imageio.ImageIO;

import java.io.File;

/**
Create a screenshot of a component.
@author Andrew Thompson
*/
class ComponentImageCapture {

  static final String HELP =
    "Type Ctrl-0 to get a screenshot of the current GUI.\n" +
    "The screenshot will be saved to the current " +
    "directory as 'screenshot.png'.";

  public static BufferedImage getScreenShot(
    Component component) {

    BufferedImage image = new BufferedImage(
      component.getWidth(),
      component.getHeight(),
      BufferedImage.TYPE_INT_RGB
      );
    // call the Component's paint method, using
    // the Graphics object of the image.
    component.paint( image.getGraphics() ); // alternately use .printAll(..)
    return image;
  }

  public static void main(String[] args) {
    Runnable r = new Runnable() {
      public void run() {
        final JFrame f = new JFrame("Test Screenshot");

        JMenuItem screenshot =
          new JMenuItem("Screenshot");
        screenshot.setAccelerator(
          KeyStroke.getKeyStroke(
            KeyEvent.VK_0,
            InputEvent.CTRL_DOWN_MASK
          ));
        screenshot.addActionListener(
          new ActionListener(){
            public void actionPerformed(ActionEvent ae) {
              BufferedImage img = getScreenShot(
                f.getContentPane() );
              JOptionPane.showMessageDialog(
                null,
                new JLabel(
                  new ImageIcon(
                    img.getScaledInstance(
                      img.getWidth(null)/2,
                      img.getHeight(null)/2,
                      Image.SCALE_SMOOTH )
                    )));
              try {
                // write the image as a PNG
                ImageIO.write(
                  img,
                  "png",
                  new File("screenshot.png"));
              } catch(Exception e) {
                e.printStackTrace();
              }
            }
          } );
        JMenu menu = new JMenu("Other");
        menu.add(screenshot);
        JMenuBar mb = new JMenuBar();
        mb.add(menu);
        f.setJMenuBar(mb);

        JPanel p = new JPanel( new BorderLayout(5,5) );
        p.setBorder( new TitledBorder("Main GUI") );
        p.add( new JScrollPane(new JTree()),
          BorderLayout.WEST );
        p.add( new JScrollPane( new JTextArea(HELP,10,30) ),
          BorderLayout.CENTER );

        f.setContentPane( p );
        f.pack();
        f.setLocationRelativeTo(null);
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setVisible(true);
      }
    };
    SwingUtilities.invokeLater(r);
  }
}

另见

上面显示的代码假定组件在渲染之前已在屏幕上实现。

Rob Camick展示了如何在Screen Image类中绘制未实现的组件。

另一个可能与此相关的主题是Render JLabel，没有第一个显示，特别是Darryl Burke的“一个行修复”。

LabelRenderTest.java

这是第二个链接上显示的代码的更新后的变体。

import java.awt.*;
import java.awt.image.BufferedImage;
import javax.swing.*;

public class LabelRenderTest {

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

            String title = "<html><body style="width: 200px; padding: 5px;'>"
                + "<h1>Do U C Me?</h1>"
                + "Here is a long string that will wrap.  "
                + "The effect we want is a multi-line label.";

                JFrame f = new JFrame("Label Render Test");
                f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

                BufferedImage image = new BufferedImage(
                    400,
                    300,
                    BufferedImage.TYPE_INT_RGB);
                Graphics2D imageGraphics = image.createGraphics();
                GradientPaint gp = new GradientPaint(
                    20f,
                    20f,
                    Color.red,
                    380f,
                    280f,
                    Color.orange);
                imageGraphics.setPaint(gp);
                imageGraphics.fillRect(0, 0, 400, 300);

                JLabel textLabel = new JLabel(title);
                textLabel.setSize(textLabel.getPreferredSize());

                Dimension d = textLabel.getPreferredSize();
                BufferedImage bi = new BufferedImage(
                    d.width,
                    d.height,
                    BufferedImage.TYPE_INT_ARGB);
                Graphics g = bi.createGraphics();
                g.setColor(new Color(255, 255, 255, 128));
                g.fillRoundRect(
                    0,
                    0,
                    bi.getWidth(f),
                    bi.getHeight(f),
                    15,
                    10);
                g.setColor(Color.black);
                textLabel.paint(g);
                Graphics g2 = image.getGraphics();
                g2.drawImage(bi, 20, 20, f);

                ImageIcon ii = new ImageIcon(image);
                JLabel imageLabel = new JLabel(ii);

                f.getContentPane().add(imageLabel);
                f.pack();
                f.setLocationByPlatform(true);

                f.setVisible(true);
            }
        });
    }
}

Swing：获取JFrame的图像

相关阅读

相关文章

相关问答

相关工具

相关文档