al_color_rgb_to_hsl - Allegro 5 API

       Given  an  RGB  triplet  with  components  in  the  range 0..1, return the hue in degrees from 0..360 and
       saturation and lightness in the range 0..1.

       al_color_rgb_to_hsl - Allegro 5 API

al_color_hsl_to_rgb(3alleg5), al_color_hsl(3alleg5)

Allegro reference manual                                                            al_color_rgb_to_hsl(3alleg5)

              #include <allegro5/allegro_color.h>

              void al_color_rgb_to_hsl(float red, float green, float blue,
                 float *hue, float *saturation, float *lightness)