code: protected BufferedImage create_FOREGROUND_Image(final int WIDTH) {
          switch (getFrameType()) {
              case ROUND:
                  return FOREGROUND_FACTORY.createRadialForeground(WIDTH);
              case SQUARE:
                  return FOREGROUND_FACTORY.createLinearForeground(WIDTH, WIDTH);
              default:
                  return FOREGROUND_FACTORY.createRadialForeground(WIDTH);
          }
      }
docs: Returns the image of the glasseffect with a centered knob
  @param WIDTH
  @return the foreground image that will be used (in principle only the glass effect)