OpenJDK, 4K display and text quality

Question

I'm using an 4K display here with 175% scaling and Windows 11. I have a Java application that writes text to a bitmap and displays this bitmap. The text quality is fine and very smooth with an Java 1.8.0_371. And all OpenJDK versions I've tried all produce a poorer and pixelated output as you can see in the images:

Is there a way to improve the quality of the text?

Sourcecode is:

package 4ktest;

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

public class TestWindow1 extends JPanel {

  private BufferedImage image;

  public TestWindow1(String text) {
      image = new BufferedImage(600, 100, BufferedImage.TYPE_INT_ARGB);

      Graphics2D g2d = image.createGraphics();
      g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
      g2d.setColor(Color.WHITE);
      g2d.fillRect(0, 0, image.getWidth(), image.getHeight());
      g2d.setColor(Color.BLACK);
      g2d.setFont(new Font("Times New Roman", Font.PLAIN, 50));      
      g2d.drawString(text, 10, 50);
      g2d.dispose();
  }

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

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

Answer 1

I could reproduce the problem, and I was able to fix the problem by using rendering hints in the paintComponent method.

public static void highQualityRenderingHints(Graphics2D g2d){
        g2d.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_COLOR_RENDERING, RenderingHints.VALUE_COLOR_RENDER_QUALITY);
        g2d.setRenderingHint(RenderingHints.KEY_FRACTIONALMETRICS, RenderingHints.VALUE_FRACTIONALMETRICS_ON);
        g2d.setRenderingHint(RenderingHints.KEY_RENDERING, RenderingHints.VALUE_RENDER_QUALITY);
        g2d.setRenderingHint(RenderingHints.KEY_TEXT_ANTIALIASING, RenderingHints.VALUE_TEXT_ANTIALIAS_ON);
    }

Calling that method on the Graphics provided in the paintComponent method.

I checked and the only hint that was needed to show the improvement wasRenderingHints.KEY_RENDERING