if ((pixelNr / w) > w) System.out.println("Error: pixelNr = " + pixelNr);
	public int getGrayscaleValue(int pixelNr) {		int w = getWidth();		if ((pixelNr / w) > w)			System.out.println("Error: pixelNr = " + pixelNr);		return getGrayscaleValue(pixelNr % w, pixelNr / w);	}