code: def setImageItem(self, img):
          
          self.imageItem = weakref.ref(img)
          img.sigImageChanged.connect(self.imageChanged)
          img.setLookupTable(self.getLookupTable)  ## send function pointer, not the result
          #self.gradientChanged()
          self.regionChanged()
          self.imageChanged(autoLevel=True)
docs: Set an ImageItem to have its levels and LUT automatically controlled
          by this HistogramLUTItem.