JTextAreaの背景に画像を表示

class CentredBackgroundBorder implements Border {
  private final Insets insets = new Insets(0, 0, 0, 0);
  private final BufferedImage image;

  public CentredBackgroundBorder(BufferedImage image) {
    this.image = image;
  }

  @Override public void paintBorder(
      Component c, Graphics g, int x, int y, int width, int height) {
    int cx = x + (width - image.getWidth()) / 2;
    int cy = y + (height - image.getHeight()) / 2;
    Graphics2D g2 = (Graphics2D) g.create();
    g2.drawRenderedImage(image, AffineTransform.getTranslateInstance(cx, cy));
    g2.dispose();
  }

  @Override public Insets getBorderInsets(Component c) {
    return insets;
  }

  @Override public boolean isBorderOpaque() {
    return true;
  }
}