gtk-rgb-to-hsv (r g b)

r -- a double float red component
g -- a double float green component
b -- a double float blue component

h -- the double float hue component
s -- the double float saturation component
v -- the double float value component

Converts a color from RGB space to HSV. Input values must be in the [0.0, 1.0] range; output values will be in the same range.