Electronic device and method for enhancing readibility of an image thereof

An electronic device is provided, which includes a light sensor, an algorithm engine, an adjustment engine, and a display. The light sensor detects an ambient brightness around the electronic device. The algorithm engine is coupled to the light sensor. The algorithm engine determines at least one adjustment function according to the ambient brightness. The adjustment engine is coupled to the algorithm engine. The adjustment engine adjusts the luminance component of each pixel of an image according to the at least one adjustment function to enhance the brightness and/or the contrast of the image. The display is coupled to the adjustment engine for displaying the adjusted image.