public void setValueAt(Object value, int rowIndex, int columnIndex) {
		Overlay overlay = overlays.get(rowIndex);
		switch (columnIndex) {
			case 0: overlay.setVisible((Boolean) value); break;
			case 1: overlay.setColor((Color) value); break;
			case 2: overlay.setName((String) value); break;
			case 3: overlay.setAlpha((Double) value); break;
			default: return;
		}
		fireTableCellUpdated(rowIndex, columnIndex);
	}