OpenJDK在4K高缩放Windows11环境下文本渲染质量优化求助

在Windows 11搭配4K显示器并设置175%缩放的环境中，Java 8能正常渲染清晰的Bitmap文本，但OpenJDK 11、22等版本会出现像素化模糊，可通过以下方案优化：

一、补充文本渲染相关的RenderingHints #

仅开启基础抗锯齿不足以适配高DPI，需添加针对性的文本渲染提示：

g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);
g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);

• VALUE_TEXT_ANTIALIAS_LCD_HRGB：针对LCD显示器优化文本抗锯齿，比普通抗锯齿更适配高DPI场景
• VALUE_FRACTIONALMETRICS_ON：启用分数度量，避免文本布局时的像素强制对齐导致模糊

二、创建适配高DPI的BufferedImage #

固定尺寸创建Bitmap会忽略系统缩放比例，改用屏幕GraphicsConfiguration生成适配实际像素的Bitmap：

// 替换原BufferedImage创建逻辑
GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
float scale = Toolkit.getDefaultToolkit().getScreenResolution() / 96.0f;
int scaledWidth = (int) Math.round(600 * scale);
int scaledHeight = (int) Math.round(100 * scale);
image = gc.createCompatibleImage(scaledWidth, scaledHeight, Transparency.TRANSLUCENT);

绘制文本时同步按缩放比例调整字体大小和坐标：

g2d.setFont(new Font("Times New Roman", Font.PLAIN, (int) Math.round(50 * scale)));
g2d.drawString(text, (int) Math.round(10 * scale), (int) Math.round(50 * scale));

最后在paintComponent中按原始逻辑尺寸绘制缩放后的Bitmap：

@Override
protected void paintComponent(Graphics g) {
    super.paintComponent(g);
    g.drawImage(image, 0, 0, 600, 100, this);
}

三、设置高DPI适配的JVM系统属性 #

在启动应用时添加以下参数，强制OpenJDK识别系统高DPI缩放：

-Dsun.java2d.dpiaware=true
-Djdk.awt.allowPixelScale=true
-Dsun.java2d.uiScale=auto

其中sun.java2d.uiScale=auto会自动适配系统缩放比例，无需手动计算缩放因子。

修改后的完整代码 #

package 4ktest;

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

public class TestWindow1 extends JPanel {

    private BufferedImage image;
    private final float scale;

    public TestWindow1(String text) {
        scale = Toolkit.getDefaultToolkit().getScreenResolution() / 96.0f;
        GraphicsConfiguration gc = GraphicsEnvironment.getLocalGraphicsEnvironment().getDefaultScreenDevice().getDefaultConfiguration();
        int scaledWidth = (int) Math.round(600 * scale);
        int scaledHeight = (int) Math.round(100 * scale);
        image = gc.createCompatibleImage(scaledWidth, scaledHeight, Transparency.TRANSLUCENT);

        Graphics2D g2d = image.createGraphics();
        // 配置完整渲染提示
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_LCD_HRGB);
        g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);

        g2d.setColor(Color.WHITE);
        g2d.fillRect(0, 0, image.getWidth(), image.getHeight());
        g2d.setColor(Color.BLACK);
        // 按缩放比例调整字体与绘制坐标
        g2d.setFont(new Font("Times New Roman", Font.PLAIN, (int) Math.round(50 * scale)));
        g2d.drawString(text, (int) Math.round(10 * scale), (int) Math.round(50 * scale));
        g2d.dispose();
    }

    @Override
    protected void paintComponent(Graphics g) {
        super.paintComponent(g);
        g.drawImage(image, 0, 0, 600, 100, this);
    }

    public static void main(String[] args) {
        // 设置高DPI适配属性
        System.setProperty("sun.java2d.dpiaware", "true");
        System.setProperty("jdk.awt.allowPixelScale", "true");
        System.setProperty("sun.java2d.uiScale", "auto");

        SwingUtilities.invokeLater(() -> {
            JFrame frame = new JFrame("Text to Bitmap");
            frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
            frame.setSize(600, 150);
            TestWindow1 panel = new TestWindow1("Version " + System.getProperty("java.version"));
            frame.add(panel);
            frame.setVisible(true);
        });
    }
}

内容的提问来源于stack exchange，提问作者Klaus Friese