import java.awt.geom.*;

static BufferedImage makeRoundedCorner(BufferedImage image, int cornerRadius) {
  int w = image.getWidth();
  int h = image.getHeight();
  BufferedImage output = new BufferedImage(w, h, BufferedImage.TYPE_INT_ARGB);
  Graphics2D g2 = output.createGraphics();

  // fake soft-clipping by first drawing the desired clip shape
  // in fully opaque white with antialiasing enabled...
  g2.setComposite(AlphaComposite.Src);
  g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
  g2.setColor(Color.WHITE);
  g2.fill(new RoundRectangle2D.Float(0, 0, w, h, cornerRadius, cornerRadius));

  // ... then compositing the image on top,
  // using the white shape from above as alpha source
  g2.setComposite(AlphaComposite.SrcAtop);
  g2.drawImage(image, 0, 0, null);
  g2.dispose();
  ret output;
}