I am having an issue with a custom drawn image rendered on the JPanel with Graphics2D. If I try to draw a 1×1 pixel for every x/y the width and length of the panel with fillRect it will create a bunch of different sized rects of 1×1, 1×2, and 2×2 in a pattern. I’ve tried playing with the Graphics2D rendering hints but could not figure out what is causing this to happen.

Here is a zoomed in view of what is happening, the rect sizing appears to create a pattern as well.

Here is a minimally viable example that should be printing 1×1 rects.

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

class Scratch {

    public static final int WIDTH = 400;
    public static final int HEIGHT = 400;

    public static void main(String[] args) {
        BufferedImage img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_4BYTE_ABGR);
        Graphics2D g2d = img.createGraphics();

        JPanel panel = new JPanel() {
            public void paintComponent(Graphics g) {
                super.paintComponent(g);
                Graphics2D panel2d = (Graphics2D) g;

                // Black bg
                g2d.setColor(Color.BLACK);
                g2d.fillRect(0, 0, getWidth(), getHeight());

                int c = 0;
                for (int x = 0; x < getWidth(); x++) {
                    for (int y = 0; y < getHeight(); y++) {
                        g2d.setColor(new Color((c += 13) % 255, (c += 17) % 255, (c += 23) % 255));
                        g2d.fillRect(x, y, 1, 1);
                    }
                }

                panel2d.drawImage(img, null, 0, 0);
            }
        };

        JFrame frame = new JFrame("Scratch");
        frame.setLayout(new BorderLayout());
        frame.add(panel, BorderLayout.CENTER);
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        frame.setResizable(false);
        frame.setVisible(true);

        frame.getContentPane().setPreferredSize(new Dimension(WIDTH, HEIGHT));
        frame.pack();
    }

}

Or should I be using something other than Graphics2D to do this?