code: def png(self):
          
          use_plugin('freeimage')
          with TemporaryFilePath(suffix='.png') as tmp:
              safe_range_im = 255 * normalise(self)
              imsave(tmp.fpath, safe_range_im.astype(np.uint8))
              with open(tmp.fpath, 'rb') as fh:
                  return fh.read()
docs: Return png string of image.