code: public void saveSpectrogram(Spectrogram spectrogram, String filename) throws IOException {
  
      BufferedImage bufferedImage = renderSpectrogram(spectrogram);
      saveSpectrogram(bufferedImage, filename);
    }
docs: Render a spectrogram of a wave file
  
  @param spectrogram spectrogram object
  @param filename output file
  @throws IOException
  @see RGB graphic rendered