1. A liquid crystal display, comprising: a plurality of pixel array areas, each pixel array area including plural pixels; a signal generation unit for generating grey-level signals corresponding to the pixels based on input image data; a weighting conversion unit for converting the grey-level signals corresponding to the pixels into a plurality of weightings; a weighting processing unit for generating a weighting sum by summing up the weightings corresponding to the pixel array area; an inversion-mode setting unit for outputting a selection signal according to the weighting sum; a polarity control unit for providing a plurality of polarity control signals; a multiplexer for selecting one polarity control signal corresponding to a weighting range into which the weighting sum falls according to the selection signal; and a data signal output unit for providing a plurality of data signals to be written into the pixel array area based on a polarity inversion mode under control of the selected polarity control signal.