al_color_lch - Allegro 5 API

       Return an ALLEGRO_COLOR(3alleg5) structure from CIE LCH values.  LCH colors are very similar to HSL, with
       the same meaning of L and H and C corresponding to S. However LCH is more visually uniform.  Furthermore,
       this function expects the angle for H in radians and not in degree.

       The  CIE  LCH  color space is a cylindrical representation of the L*a*b* color space.  The L component is
       the same and C and H are computed like this:

              C = sqrt(a * a + b * b)
              H = atan2(b, a)

       al_color_lch - Allegro 5 API

al_color_lch_to_rgb(3alleg5), al_color_rgb_to_lch(3alleg5)

Allegro reference manual                                                                   al_color_lch(3alleg5)

       5.2.3

              #include <allegro5/allegro_color.h>

              ALLEGRO_COLOR al_color_lch(float l, float c, float h)