Why is image printed from Java fuzzy?

Question

I have an application which heavily leverages swing components, using JButtons and JLabels within a JPanel. I use a GridBagLayout to layout these components, and on screen they display just fine. Running on windows if that matters.

The problem I have been struggling with has to do with the clarity of the printed image, whether this is printed to paper, or a jpg. The image tends to look muddy. The edges of buttons, the text within buttons or labels, even straight lines look fuzzy.

Below is an example that generates a 50x50 jpg which contains a 40x40 rectangle inside of it. There seems to be a faint shadow line inside and outside of the rectangle, faint dots at the corners, and even the edges of the line seem fuzzy. I see the same results with swing components too.

In my searching and reading, I've found a lot of references to RenderingHints, but I've seen too many suggestions of the form "try setting this" without any explanation to discern which hint(s) might apply.

Any suggestions/pointers would be appreciated.

import java.lang.*;
import java.awt.*;
import javax.swing.*;
import java.awt.event.*;
import java.awt.image.*;
import javax.imageio.ImageIO;
import java.io.*;

public class MyFrame extends JFrame {

  public static void main(String[] args) {

     new MyFrame(); 

  }

  MyFrame() {
      JButton button;

      button = new JButton("print jpg");

      button.addActionListener( new ActionListener() {
         public void actionPerformed(ActionEvent evt) {
               takePicture();
         }
      });

      setDefaultCloseOperation(JFrame.DISPOSE_ON_CLOSE);

      add(button);

      pack();
      setVisible(true);

  }

  void takePicture() {

    BufferedImage img = new BufferedImage(50, 50, BufferedImage.TYPE_INT_RGB);
    Graphics g = img.getGraphics();

    g.setColor(Color.white);
    g.fillRect(0,0,50,50);

    g.setColor(Color.black);
    g.drawRect(5,5,40,40);

    try {
      ImageIO.write(img, "jpg", new File("output_file.jpg") );
    }
    catch (IOException e) {
      e.printStackTrace();
    }

  }
}

Answer 1

What you see is probably JPEG compression artifacts. If you will use some lossless format (like PNG), you'll get the desired image.

Here's the version that outputs perfectly crisp rectangle:

import java.awt.*;
import java.awt.image.*;
import javax.imageio.ImageIO;
import java.io.*;

public class PrintImage {
    public static void main(String[] args) throws Exception {
        BufferedImage img = new BufferedImage(50, 50, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = (Graphics2D) img.getGraphics();

        g.setColor(Color.white);
        g.fillRect(0,0,50,50);

        g.setColor(Color.black);
        g.drawRect(5,5,40,40);

        ImageIO.write(img, "png", new File("output_file.png") );
    }
}

Note that I used png as output format - it doesn't lose information to save space, unlike jpg.

Also make sure that your image viewer doesn't try to interpolate pixels when you zoom in - or else you'll see blurry lines. Image editing software usually doesn't do that, so you can use Paint to check that you indeed have the desired image.