悬停时在 JFrame 上增亮图像（JLabel）

Question

我在 JFrame 上有一个 JLabel 图像，我想在悬停时太亮，尝试了一些方法，但似乎没有任何效果，这是我当前的代码：

public class DivinationLogo extends JLabel {
private BufferedImage logo;
public DivinationLogo() {

    super();
    try {
        logo = ImageIO.read(getClass().getResourceAsStream("/assets/images/logo.png"));
    } catch (IOException e) {
        e.printStackTrace();
    }
   // setIcon(new ImageIcon(logo));
    setIconTextGap(0);
    setBorder(null);
    setText(null);

    addMouseListener(new MouseAdapter() {
        @Override
        public void mouseClicked(MouseEvent e) {
            Functions.openWebPage(Config.website);
        }

        @Override
        public void mouseEntered(MouseEvent e) {
           Functions.brightnessControl(logo, .3F);
        }

        @Override
        public void mouseExited(MouseEvent e) {
            Functions.brightnessControl(logo, 1.0F);
        }
    });
    setBounds(-5, 1, 247, 106);
}

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.drawImage(logo, -5, 1, null);
 }
}

Functions.brightnessControl：

public static Image brightnessControl(Image image, float brightness) {
    BufferedImage bi = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB);
    Graphics bg = bi.getGraphics();

    if (bi.getColorModel().hasAlpha()) {
        System.out.println("Image has got an alpha channel");
    }

    bg.drawImage(image, 0, 0, null);
    bg.dispose();
    RescaleOp rescaleOp = new RescaleOp(brightness, 0, null);
    rescaleOp.filter(bi, bi);
    image = bi;
    return bi;
}

目前，它没有做任何让我感到困惑的事情。如果有人知道这是如何实现的，请随时告诉我:)

Answer 1

好的，所以基本思路是，当鼠标进入组件时，你想生成一个“亮”版本的组件（我知道，很明显，但请耐心等待）

问题是，你有一个Graphics 上下文并且你需要一个图像：/

以下内容并未过度优化，但无需花费大量时间添加PropertyChange 支持，这将为您提供基本思路。

import java.awt.EventQueue;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.GridBagLayout;
import java.awt.Image;
import java.awt.event.MouseAdapter;
import java.awt.event.MouseEvent;
import java.awt.image.BufferedImage;
import java.awt.image.RescaleOp;
import java.io.IOException;
import javax.imageio.ImageIO;
import javax.swing.ImageIcon;
import javax.swing.JFrame;
import javax.swing.JLabel;

class Main {

    public static void main(String[] args) {
        new Main();
    }

    public Main() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    JFrame frame = new JFrame();
                    frame.setLayout(new GridBagLayout());
                    JLabel label = new BrightLabel();
                    label.setIcon((new ImageIcon(ImageIO.read(Main.class.getResource("background.png")))));
                    frame.add(label);
                    frame.pack();
                    frame.setLocationRelativeTo(null);
                    frame.setVisible(true);
                } catch (IOException ex) {
                    ex.printStackTrace();
                }
            }
        });
    }

    public class BrightLabel extends JLabel {

        private MouseAdapter mouseHandler;
        private boolean isHover = false;

        @Override
        public void addNotify() {
            super.addNotify();
            mouseHandler = new MouseAdapter() {
                @Override
                public void mouseEntered(MouseEvent e) {
                    isHover = true;
                    repaint();
                }

                @Override
                public void mouseExited(MouseEvent e) {
                    isHover = false;
                    repaint();
                }
            };

            System.out.println("...");
            addMouseListener(mouseHandler);
        }

        @Override
        public void removeNotify() {
            super.removeNotify();
            if (mouseHandler != null) {
                removeMouseListener(mouseHandler);
            }
            mouseHandler = null;
        }

        @Override
        protected void paintComponent(Graphics g) {
            if (!isHover) {
                super.paintComponent(g);
                return;
            }

            BufferedImage img = new BufferedImage(getWidth(), getHeight(), BufferedImage.TYPE_INT_ARGB);
            Graphics2D g2d = img.createGraphics();
            super.paintComponent(g2d);
            g2d.dispose();

            Image bright = brightnessControl(img, 1.3f);
            g.drawImage(bright, 0, 0, this);
        }

        public Image brightnessControl(Image image, float brightness) {
            BufferedImage bi = new BufferedImage(image.getWidth(null), image.getHeight(null), BufferedImage.TYPE_INT_ARGB);
            Graphics bg = bi.getGraphics();

            if (bi.getColorModel().hasAlpha()) {
                System.out.println("Image has got an alpha channel");
            }

            bg.drawImage(image, 0, 0, null);
            bg.dispose();
            RescaleOp rescaleOp = new RescaleOp(brightness, 0, null);
            rescaleOp.filter(bi, bi);
            image = bi;
            return bi;
        }

    }

}

本质上，当鼠标进入或存在组件时，我们设置isHover属性。然后我们调用repaint 来触发新的绘制通道。

绘制组件时，如果isHover是true，我们稍微接管绘制过程，生成自己的缓冲区并将组件绘制到它。这给了我们我们的基本图像。从那里我们使图像变亮并将其绘制到Graphics 上下文

Answer 2

java 中的参数是按值传递的，因此您必须使图像变亮的函数不会对传递给它的图像产生影响。

更改图像后，您错过了 repaint() 调用。

您绝对不想每次将鼠标悬停在图像上时都准备悬停图像。在构造函数中预先计算悬停并将其分配给单独的图像。

如果悬停为真，则创建一个成员变量，并在paint方法中使用它来确定要绘制的图像。