code: def image(self):
          
          if not hasattr(self, 'ren_win') and hasattr(self, 'last_image'):
              return self.last_image
          ifilter = vtk.vtkWindowToImageFilter()
          ifilter.SetInput(self.ren_win)
          ifilter.ReadFrontBufferOff()
          if self.image_transparent_background:
              ifilter.SetInputBufferTypeToRGBA()
          else:
              ifilter.SetInputBufferTypeToRGB()
          return self._run_image_filter(ifilter)
docs: Returns an image array of current render window