'Extract the data from the live signal'

def _getBestValue(self, img):

    if self._extractor:
        mc = self._extractor(img)
    else:
        temp = self._roi.reassign(img)
        mc = temp.meanColor()
    if (self._bestKey == 'r'):
        return mc[0]
    elif (self._bestKey == 'g'):
        return mc[1]
    elif (self._bestKey == 'b'):
        return mc[2]
    elif (self._bestKey == 'i'):
        return Color.getLightness(mc)
    elif (self._bestKey == 'h'):
        return Color.getHueFromRGB(mc)
