Dimming the LCD backlight saves the battery power of a portable multimedia device but causes image quality degradation. In this paper, we propose an algorithm to overcome the effect of dim backlight on image quality. This algorithm enhances the backlight-scaled image by exploiting the human visual property. It performs a two-layer image decomposition based on the just noticeable difference theory and enhances the backlight-scaled image by luminance boosting and compression. Experimental results are provided to demonstrate the performance of the proposed algorithm.