Base64エンコーダを使用して画像を文字列に変換する

JButton encode = new JButton("encode");
encode.addActionListener(e -> {
  JFileChooser chooser = new JFileChooser();
  chooser.addChoosableFileFilter(
      new FileNameExtensionFilter("PNG (*.png)", "png"));
  int retvalue = chooser.showOpenDialog(encode);
  if (retvalue == JFileChooser.APPROVE_OPTION) {
    Path path = chooser.getSelectedFile().toPath();
    try {
      textArea.setText(
          Base64.getEncoder().encodeToString(Files.readAllBytes(path)));
    } catch (IOException ex) {
      ex.printStackTrace();
    }
  }
});

JButton decode = new JButton("decode");
decode.addActionListener(e -> {
  String b64 = textArea.getText();
  if (b64.isEmpty()) {
    return;
  }
  // byte[] bytes = b64.getBytes(StandardCharsets.ISO_8859_1);
  // try (InputStream input = new ByteArrayInputStream(
  //     Base64.getDecoder().decode(bytes))) {
  try (InputStream input = new ByteArrayInputStream(Base64.getDecoder().decode(b64))) {
    label.setIcon(new ImageIcon(ImageIO.read(input)));
  } catch (IOException ex) {
    ex.printStackTrace();
  }
});