def negate(self, grayscale=False, channel=None):
        if channel:
            try:
                ch_const = CHANNELS[channel]
            except KeyError:
                raise ValueError(repr(channel) + ' is an invalid channel type'
                                 '; see wand.image.CHANNELS dictionary')
            r = library.MagickNegateImageChannel(self.wand, ch_const,
                                                 grayscale)
        else:
            r = library.MagickNegateImage(self.wand, grayscale)
        if not r:
            self.raise_exception()
Generator of spectrum frames
dataset/ETHPy150Open dahlia/wand/wand/image.py/BaseImage.negate--crossover with--dataset/ETHPy150Open dongying/dear/dear/spectrum/_base.py/SpectrumBase.walk