'**SUMMARY**
Invert the filter. All values will be subtracted from 255.
**RETURNS**
Inverted Filter
**EXAMPLE**
>>> flt = DFT.createGaussianFilter()
>>> invertflt = flt.invert()'

def invert(self):

    flt = self._numpy
    flt = (255 - flt)
    img = Image(flt)
    invertedfilter = DFT(numpyarray=flt, image=img, size=self.size(), type=self._type)
    invertedfilter._updateParams(self)
    return invertedfilter
