1. A method for mapping an input grayscale into an output luminance comprising: selecting a reference grayscale and a curvature according to an input grayscale; and generating an output luminance according to the reference grayscale, the curvature, and the input grayscale, wherein the output luminance is generated by computing an equation of: Y=A*(X 2 )−A*(X′)*X, wherein Y denotes the output luminance, A denotes the curvature, X denotes the input grayscale, and X′ denotes the reference grayscale.