@Override
	protected void paintIcon( Component c, Graphics2D g ) {
		paintBackground( c, g );

		g.setColor( c.getForeground() );

		int x = (width / 2) - 4;
		int y = (height / 2) - 4;
		Path2D r1 = FlatUIUtils.createRectangle( x + 1, y - 1, 8, 8, 1 );
		Path2D r2 = FlatUIUtils.createRectangle( x - 1, y + 1, 8, 8, 1 );

		Area area = new Area( r1 );
		area.subtract( new Area( new Rectangle2D.Float( x - 1, y + 1, 8, 8 ) ) );
		g.fill( area );

		g.fill( r2 );
	}
"restore" (or "minimize") icon for {@link javax.swing.JInternalFrame}.

@author Karl Tauber
flatlaf-core/src/main/java/com/formdev/flatlaf/icons/FlatInternalFrameRestoreIcon.java