1. A method for generating a gamma table, applied to a display, the display obtaining n-bit corrected gray levels [y(1),. .. , y(2 m )] from m-bit original gray levels [x(1),. .. , x(2 m )] by using the gamma table, m and n being positive integers, the method comprising: (a) calculating a plurality of corrected gray levels [y(1),. .. , y(2 m )] corresponding to the original gray levels [x(1),. .. , x(2 m )] according to a gamma curve; (b) calculating gray-level differences w(i)={(y(i+1)−y(i)), i=1,3,. .. } or {(y(i)−y(i+1)), i=1,3,. .. } of two adjacent corrected gray levels y(i) and y(i+1) (i=1,3,. .. ); and (c) respectively recording the n-bit corrected gray levels y(i) and the k-bit gray-level differences w(i) (i=1,3,. .. ) as (n+k)-bit gamma reference values z(i) (i=1,3,. .. ) corresponding to the odd-order original gray levels x(i) (i=1,3,. .. ) in order to generate the gamma table, wherein k is a positive integer.