Generate a complementary colour using the HSLuv colour space

generate_complementary.py

# Generate colours which work well together

# Reference
# https://www.kuon.ch/post/2020-03-08-hsluv/
# https://www.boronine.com/2012/03/26/Color-Spaces-for-Human-Beings/
# https://github.com/hsluv/hsluv-python

import hsluv

# Some simple constants
R, G, B = 0, 1, 2
L, U, V = 0, 1, 2

# The angle to shift the color to produce its complementary
COMPLEMENTARY = 180.0

# Some utility functions
def scale(rgb):
    return [rgb[R]/100.0, rgb[G]/100.0, rgb[B]/100.0]

def descale(rgb):
    return [round(rgb[R]*100.0, 1), round(rgb[G]*100.0, 1), round(rgb[B]*100.0, 1)]

# The function generates a complementary colour (with the same perceptual
# brightness and saturation) as the given RGB (from GIMP for example)
# NB: each component goes from 0.0 to 100.0 (GIMP style)
def generate_complementary(rgb_color):
    print("rbg", rgb_color)
    rgb_color = scale(rgb_color)
    
    # The corresponding HSLuv
    hsluv_color = hsluv.rgb_to_hsluv(rgb_color)
    print("hsluv", hsluv_color)

    # A complementary colour created by shifting the L component by 180 degrees
    hsluv_color_complementary = hsluv_color[:]

    if (hsluv_color_complementary[L] < COMPLEMENTARY):
        hsluv_color_complementary[L] += COMPLEMENTARY
    else:
        hsluv_color_complementary[L] -= COMPLEMENTARY

    print("hsluv complementary", hsluv_color_complementary)

    # And converted to RGB
    rgb_color_complementary = hsluv.hsluv_to_rgb(hsluv_color_complementary)
    rgb_color_complementary = descale(rgb_color_complementary)
    print("rgb complementary", rgb_color_complementary)
    
    
# From GIMP -- hsluv expects components from 0 to 1
generate_complementary([96.6,63.1,10.2])