Display device and method

A region-based image display device includes a backlight module, a separating unit, a signal-processing unit, and a modulation unit. The backlight module includes several backlight regions. Each backlight region includes an adjustable luminance unit. Each luminance unit has a basis luminance value. The separating unit separates an input image signal into several image region signals corresponding to the backlight regions. The signal-processing unit transforms the image region signals into several output image signals. The modulation unit adjusts the basis luminance values to output luminance values according to the image region signals. Each basis luminance value and the corresponding image region signal on the one hand, and the corresponding output luminance value and output image signal, on the other hand, cooperatively define substantially the same chromaticity and brightness.