如何将图标从 JLabel 转换为 BufferedImage？

Posted 2023-02-16

【中文标题】如何将图标从 JLabel 转换为 BufferedImage？

【英文标题】：How to convert Icon from JLabel into BufferedImage?

【发布时间】：2011-09-16 03:00:24

【问题描述】：

简单，非常直截了当，但我和谷歌叔叔似乎感到困惑。

我有一个 JLabel 已经有自己的 Icon。

如何将JLabel得到的Icon转换成BufferedImage？

有什么办法吗：我试着像这样多次casting ..

 final BufferedImage bf1 = (BufferedImage)((Image)jll_img.getIcon());

..但它失败了。

【参考方案1】：

import java.awt.*;
import java.awt.image.*;
import javax.swing.*;
import java.net.URL;

class GetImage 

    public static void main(String[] args) throws Exception 
        final String text = "Mt Stromlo at sunset";
        final URL url = new URL(
            "http://i.stack.imgur.com/lxthA.jpg");
        SwingUtilities.invokeLater(new Runnable() 
            public void run() 
                ImageIcon imageIcon = new ImageIcon(url);
                JLabel imageLabel = new JLabel(
                    text,
                    imageIcon,
                    SwingConstants.CENTER);
                JOptionPane.showMessageDialog(null, imageLabel);

                Icon icon = imageLabel.getIcon();

                BufferedImage bi = new BufferedImage(
                    icon.getIconWidth(),
                    icon.getIconHeight(),
                    BufferedImage.TYPE_INT_RGB);
                Graphics g = bi.createGraphics();
                // paint the Icon to the BufferedImage.
                icon.paintIcon(null, g, 0,0);
                g.setColor(Color.WHITE);
                g.drawString(text,10,20);
                g.dispose();

                JOptionPane.showMessageDialog(
                    null,
                    new JLabel(new ImageIcon(bi)));
            
        );
    

这里有一些来自 Sun 论坛的旧代码，用于处理在内存中创建的图像。

import java.awt.*;
import java.awt.image.BufferedImage;
import javax.imageio.ImageIO;
import java.io.ByteArrayOutputStream;
import java.util.Random;
import javax.swing.*;

class ImageCacheTest 

    private JLabel imageLabel;
    private Dimension halfScreenSize;
    private Random random;
    private JProgressBar memory;
    private Font bigFont = new Font("Arial", Font.BOLD, 30);
    private int count = 0;
    private int startMem = 0;
    private int maxMem = 0;
    private int peakMem = 0;
    private int useMem = 0;

    ImageCacheTest() 
        startMem = ((int) Runtime.getRuntime().freeMemory());
        maxMem = ((int) Runtime.getRuntime().freeMemory());
        peakMem = ((int) Runtime.getRuntime().freeMemory());
        JPanel p = new JPanel(new BorderLayout(4, 4));
        Dimension d = Toolkit.getDefaultToolkit().getScreenSize();
        halfScreenSize = new Dimension(d.width / 2, d.height / 2);
        //halfScreenSize = new Dimension(d.width - 11, d.height - 51);
        random = new Random();
        imageLabel = new JLabel(new ImageIcon(convertToFromBytes(getImage())));
        memory = new JProgressBar(0, (int) Runtime.getRuntime().maxMemory());
        p.add(imageLabel, BorderLayout.CENTER);
        p.add(memory, BorderLayout.SOUTH);
        JFrame f = new JFrame();
        f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        f.setContentPane(p);
        f.setLocation(150, 150);
        f.pack();
        f.setVisible(true);
        Runnable r = new Runnable() 

            @Override
            public void run() 
                while (true) 
                    try 
                        imageLabel.setIcon(new ImageIcon(convertToFromBytes(getImage())));
                        memory.setValue((int) Runtime.getRuntime().freeMemory());
                        useMem = ((int) Runtime.getRuntime().freeMemory());
                        Thread.sleep(30);
                     catch (InterruptedException ex) 
                        //something exceptio
                    finally
                        // alive that if required
                    
                
            
        ;
        Thread t = new Thread(r);
        t.start();
    

    private BufferedImage getImage() 
        GradientPaint gp = new GradientPaint(0f, 0f, new Color(127 + random.nextInt(128), 127 + random.nextInt(128), 127 + random.nextInt(128)),
                (float) halfScreenSize.width, (float) halfScreenSize.width, new Color(random.nextInt(128), random.nextInt(128), random.nextInt(128)));
        BufferedImage bi = new BufferedImage(halfScreenSize.width, halfScreenSize.height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g2d = bi.createGraphics();
        g2d.setPaint(gp);
        g2d.fillRect(0, 0, halfScreenSize.width, halfScreenSize.height);
        g2d.setFont(bigFont);
        g2d.setColor(Color.BLACK);
        if (maxMem < ((int) Runtime.getRuntime().freeMemory())) 
            maxMem = ((int) Runtime.getRuntime().freeMemory());
        
        if (peakMem > ((int) Runtime.getRuntime().freeMemory())) 
            peakMem = ((int) Runtime.getRuntime().freeMemory());
        
        useMem = ((int) Runtime.getRuntime().freeMemory()) - useMem;
        g2d.drawString("" + ++count, 20, 100);
        g2d.drawString("JVM memory status --->  ", 20, 195);
        g2d.drawString("tot. memory --->  " + ((int) Runtime.getRuntime().totalMemory()), 20, 240);
        g2d.drawString("max. memory --->  " + ((int) Runtime.getRuntime().maxMemory()), 20, 270);
        g2d.drawString("free on startUp --->  " + startMem, 20, 300);
        g2d.drawString("max free memory --->  " + maxMem, 20, 350);
        g2d.drawString("min free memory --->  " + peakMem, 20, 380);
        g2d.drawString("act free memory --->  " + ((int) Runtime.getRuntime().freeMemory()), 20, 410);
        g2d.drawString("usage of memory --->  " + useMem, 20, 450);
        g2d.dispose();
        return bi;
    

    /** Not entirely sure this method is necessary for indicating 'no cache',
    but since the claim was specific to byte arrays, we'll do it. */
    private Image convertToFromBytes(BufferedImage image) 
        try 
            ByteArrayOutputStream baos = new ByteArrayOutputStream();
            ImageIO.write(image, "png", baos);
            return Toolkit.getDefaultToolkit().createImage(baos.toByteArray());
         catch (Exception e) 
            return null;
        
    

    public static void main(String[] args) 
        Runnable r = new Runnable() 

            @Override
            public void run() 
                ImageCacheTest ict = new ImageCacheTest();
            
        ;
        SwingUtilities.invokeLater(r);
    

截图

该代码的屏幕截图，宽度降至 ¼ 屏幕宽度。

【讨论】：

@Andrew Thompson :-) 正如我所说，回到你的代码，你可以将你的 Goblin's-Edge-Code 添加到你的帖子中，然后我会从这个帖子中删除我的帖子，用我的尊重

@mKorbel：“您可以将 Goblin's-Edge-Code 添加到您的帖子中”。完毕。顺便说一句，喜欢这种表达方式——胜过“尖端”。 ;)

@Andrew Thompson phhhhhhhhaaa 和我一样好...，没错，谢谢

+1 好例子。不要忽略dispose() createGraphics() 返回的图形实例。

【参考方案2】：

这是最简单的方法：

labelPicture = new JLabel("Picture");
labelPicture.setIcon(new ImageIcon("picture.png"));
.
.
ImageIcon icon = (ImageIcon)labelPicture.getIcon()
BufferedImage img = (BufferedImage)((Image) icon.getImage());

【参考方案3】：

为了放大@Andrew Thompson 的answer，请注意实现Icon 接口的对象知道如何绘制某些东西，但可能还没有被要求这样做。相比之下，BufferedImage 具有“可访问的图像数据缓冲区”，您的程序必须通过调用 paintIcon() 方法来呈现它。这是一个相关的example。

【参考方案4】：

您不能将 ImageIcon 转换为 Image，因为它不是子类。不过，ImageIcon 确实有一个方法 getImage() 返回和 Image。见here

【讨论】：

注意JLabel返回的Icon不一定是ImageIcon，&Icon没有getImage()方法。此外，从ImageIcon.getImage() 返回的Image 不能保证是BufferedImage。使用我的回复中概述的方法更安全。