13.2.4.4 Modifying Saturation

The saturation of a color is the distance of that color from a gray of equal intensity.[30] Haeberli has suggested modifying saturation using the equation:

$$\left[ \begin{array}{cccc} R' \\ G' \\ B' \\ A \end{array... ...\left[ \begin{array}{c} R \\ G \\ B \\ A \end{array}\right]$$

where:

$$\begin{eqnarray*} a & = & (1 - s) * R_w + s \\ b & = & (1 - s) * R_w \\ c & = ... ...s) * B_w \\ h & = & (1 - s) * B_w \\ i & = & (1 - s) * B_w + s \end{eqnarray*}$$

with $R_w$, $G_w$, and $B_w$ as described in the above section. Since the saturation of a color is the difference between the color and a gray value of equal intensity, it is comforting to note that setting $s$ to $0$ gives the luminance equation. Setting $s$ to $1$ leaves the saturation unchanged; setting it to $-1$ takes the complement of the colors [42].