DIB's: how can i calculate saturation, bright, black and white and others?

[Cambalinho]

i'm using DIB's. i can get RGB colors easly. my problem is: how can i calculate staturation, bright and black and white?
i don't know these formulas :(
i'm sorry but the bright isn't:

bright is the x addiction:

R=R + x;
G=G + x;
B=B + x;

???