@Override public PNGImageNotebookOutput convert(Object object) { Chart chart = (Chart) object; byte[] bt; try { bt = BitmapEncoder.getBitmapBytes(chart, BitmapEncoder.BitmapFormat.PNG); Base64.getEncoder().encodeToString(bt); return new PNGImageNotebookOutput(Base64.getEncoder().encodeToString(bt)); } catch (IOException ex) { Logger.getLogger(ChartToPNGNotebookConverter.class.getName()).log(Level.SEVERE, null, ex); } return null; }