gif type file only allow to hold 256 kind of color.
Previous code check the index of code, and next generate 1 integer.
(the function name as PixelLookup)
This patch pre-calculate the result of PixelLookup.
So we can reduce the bitwise operation + ColorMap access time.
Change-Id: I31f00a6a25b6669582d4edf86b2e7bd6d621a020
Signed-off-by: Eunki, Hong <eunkiki.hong@samsung.com>