Facilmente podemos hacer resize de una imágen para un JLabel

ImageIcon image = new ImageIcon("c:/image.png");
int scale = 3;

int width = image.getIconWidth();
int height = image.getIconHeight();
BufferedImage buffer = new BufferedImage(scale * width, scale * height, BufferedImage.TYPE_INT_ARGB);
Graphics2D graphics = buffer.createGraphics();
graphics.scale(scale,scale);
image.paintIcon(null, graphics, 0, 0);
graphics.dispose();

JLabel label = new JLabel(new ImageIcon(buffer)));