code: public void setGrayContentPane(boolean gray) {
  		final BufferedImageOp bio = new ColorConvertOp(ColorSpace.getInstance(ColorSpace.CS_GRAY),
  				null);
  		((JXLayer) getContentPane()).setBufferedImageOp(gray ? bio : null);
  	}
docs: Grise ou dégrise le contentPane de la frame principale.
  @param gray boolean