Remove JTextPane's white background without setOpaque() over a translucent JFrame

Question

I have a Java code where I implemented a translucent JPanel with an image drawn on it with Graphics 2D. This image is a PNG that includes a white rectangle, 80% opaque, all over

Answer 1

to make it work with Nimbus L&F:

jta.setOpaque(false);
jta.setBorder(BorderFactory.createEmptyBorder());
jta.setBackground(new Color(0,0,0,0));

Answer 2

This is how I might approach this kind of idea...

public class OverlayTextArea {

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

    public OverlayTextArea() {
        EventQueue.invokeLater(new Runnable() {
            @Override
            public void run() {
                try {
                    UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());
                } catch (Exception ex) {
                }

                JFrame frame = new JFrame("Testing");
                frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                frame.setContentPane(new ImagePane());
                frame.setLayout(new BorderLayout());
                frame.add(new TransparentTextArea());
                frame.pack();
                frame.setLocationRelativeTo(null);
                frame.setVisible(true);
            }
        });
    }

    public class TransparentTextArea extends JTextArea {

        public TransparentTextArea() {
            setOpaque(false);
            setBorder(new CompoundBorder(new EmptyBorder(10, 10, 10, 10), new LineBorder(Color.LIGHT_GRAY)));
        }

        @Override
        protected void paintComponent(Graphics g) {
            g.setColor(new Color(255, 255, 255, 128));
            Insets insets = getInsets();
            int x = insets.left;
            int y = insets.top;
            int width = getWidth() - (insets.left + insets.right);
            int height = getHeight() - (insets.top + insets.bottom);
            g.fillRect(x, y, width, height);
            super.paintComponent(g);
        }

    }

    public class ImagePane extends JPanel {

        private BufferedImage background;

        public ImagePane() {
            try {
                background = ImageIO.read(new File("/path/to/background.img"));
            } catch (IOException ex) {
                ex.printStackTrace();
            }
        }

        @Override
        public Dimension getPreferredSize() {
            return background == null ? super.getPreferredSize() : new Dimension(background.getWidth(), background.getHeight());
        }

        @Override
        protected void paintComponent(Graphics g) {
            super.paintComponent(g);
            if (background != null) {
                int x = (getWidth() - background.getWidth()) / 2;
                int y = (getHeight() - background.getHeight()) / 2;
                g.drawImage(background, x, y, this);
            }
        }

    }

}

Feedback

• You really should call super.paintComponent, failing to do so can lead it some serious trouble, especially when you're dealing with transparent components.
• Don't perform any long running tasks within the paintXxx methods, like loading images. These methods are intended to return quickly and may be called multiple times within succession...