JDK1.4で複数画像を1つの画像にまとめたい

  File outFile;
  File outFile2;
  Date date = new Date();
  String filename = date.getTime() + "_01.png";
  String filename2 = date.getTime() + "_02.png";
  String outFileName = date.getTime() + "_out.png";
  // 画像まとめテスト
  Iterator writers = ImageIO.getImageWritersByFormatName("png");
  ImageWriter writer = (ImageWriter)writers.next();
  ImageOutputStream ios = ImageIO.createImageOutputStream(new File(outFileName));
  writer.setOutput(ios);

  // キャンパスイメージ作成
  BufferedImage canpas_image = new BufferedImage(600,600,BufferedImage.TYPE_INT_BGR);
  // Graphicsオブジェクト取得
  Graphics2D g2 = canpas_image.createGraphics();
  Image f_image,s_image;
  IIOImage iio;

  try {
    outFile = new File(filename);
    outFile2 = new File(filename2);
    f_image = ImageIO.read(outFile);
    s_image = ImageIO.read(outFile2);

    // 読み取ったイメージをキャンパスに出力
    g2.drawImage(f_image,0,0,300,300,Color.WHITE,null);
    g2.drawImage(s_image,300,0,300,300,Color.WHITE,null);

    iio = new IIOImage(canpas_image,null,null);
    writer.write(iio);
  } catch (Exception e) {
    e.printStackTrace();
  } finally {
    writer.dispose();
    ios.close();
  }

public void addNotify() {
     super.addNotify(); // これを忘れると悲惨
     image = createImage(w, h);
}