Create 9-slice scaling image JButton

• download example.jar
• download src.zip
• repository

Code

class NineSliceScalingIcon implements Icon {
  private final BufferedImage image;
  private final int leftw;
  private final int rightw;
  private final int toph;
  private final int bottomh;
  private int width;
  private int height;
  protected NineSliceScalingIcon(
      BufferedImage image, int leftw, int rightw, int toph, int bottomh) {
    this.image = image;
    this.leftw = leftw;
    this.rightw = rightw;
    this.toph = toph;
    this.bottomh = bottomh;
  }
  @Override public int getIconWidth() {
    return width; // Math.max(image.getWidth(null), width);
  }
  @Override public int getIconHeight() {
    return Math.max(image.getHeight(null), height);
  }
  @Override public void paintIcon(Component cmp, Graphics g, int x, int y) {
    Graphics2D g2 = (Graphics2D) g.create();
    g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                        RenderingHints.VALUE_ANTIALIAS_ON);
    Insets i;
    if (cmp instanceof JComponent) {
      i = ((JComponent) cmp).getBorder().getBorderInsets(cmp);
    } else {
      i = new Insets(0, 0, 0, 0);
    }

    // g2.translate(x, y); // 1.8.0: work fine?
    int iw = image.getWidth(cmp);
    int ih = image.getHeight(cmp);
    width  = cmp.getWidth() - i.left - i.right;
    height = cmp.getHeight() - i.top - i.bottom;

    g2.drawImage(
        image.getSubimage(leftw, toph, iw - leftw - rightw, ih - toph - bottomh),
        leftw, toph, width - leftw - rightw, height - toph - bottomh, cmp);
    if (leftw > 0 && rightw > 0 && toph > 0 && bottomh > 0) {
      g2.drawImage(image.getSubimage(leftw, 0, iw - leftw - rightw, toph),
                   leftw, 0, width - leftw - rightw, toph, cmp);
      g2.drawImage(image.getSubimage(leftw, ih - bottomh, iw - leftw - rightw, bottomh),
                   leftw, height - bottomh, width - leftw - rightw, bottomh, cmp);
      g2.drawImage(image.getSubimage(0, toph, leftw, ih - toph - bottomh),
                   0, toph, leftw, height - toph - bottomh, cmp);
      g2.drawImage(image.getSubimage(iw - rightw, toph, rightw, ih - toph - bottomh),
                   width - rightw, toph, rightw, height - toph - bottomh, cmp);

      g2.drawImage(image.getSubimage(0, 0, leftw, toph),
                   0, 0, cmp);
      g2.drawImage(image.getSubimage(iw - rightw, 0, rightw, toph),
                   width - rightw, 0, cmp);
      g2.drawImage(image.getSubimage(0, ih - bottomh, leftw, bottomh),
                   0, height - bottomh, cmp);
      g2.drawImage(image.getSubimage(iw - rightw, ih - bottomh, rightw, bottomh),
                   width - rightw, height - bottomh, cmp);
    }
    g2.dispose();
  }
}

References

• symbol_scale_2.jpg - Real World Illustrator: Understanding 9-Slice Scaling
• Create 9-slice scaling image JButton(Japanese)