code: public Chunk setBackground(Color color, float extraLeft, float extraBottom,
  			float extraRight, float extraTop) {
  		return setAttribute(BACKGROUND, new Object[] { color,
  				new float[] { extraLeft, extraBottom, extraRight, extraTop } });
  	}
docs: Sets the color and the size of the background <CODE>Chunk</CODE>.
  
  @param color
  the color of the background
  @param extraLeft
  increase the size of the rectangle in the left
  @param extraBottom
  increase the size of the rectangle in the bottom
  @param extraRight
  increase the size of the rectangle in the right
  @param extraTop
  increase the size of the rectangle in the top
  @return this <CODE>Chunk</CODE>