How to convert an indexed image to rgb image in C#?

hey , i want to convert an indexed image to rg开发者_Go百科b image in C#

Use a palette (a sort of conversion table). i.e.:

i  ->  R,G,B
0     255, 0, 0
1     254, 0, 0
2     253, 0, 0
3     252, 0, 0
4     251, 0, 0
.
.
260   0, 250, 0
.
.
.

etc