Extract a black/white accent for a .colorset/Contents.json color

colorset_to_accent.py

import json
from typing import Any, Tuple

type RGB = Tuple[int, int, int]
type RGBA = Tuple[int, int, int, int]


def rgba_to_rgb(foreground: RGBA, background: RGB) -> RGB:
    (fg_r, fg_g, fg_b, fg_a) = foreground
    (bg_r, bg_g, bg_b) = background
    a = fg_a / 255
    inv_a = 1 - a
    return (
        round(inv_a * bg_r + a * fg_r),
        round(inv_a * bg_g + a * fg_g),
        round(inv_a * bg_b + a * fg_b),
    )


def sRGB(c: int) -> float:
    c_ = c / 255
    if c_ <= 0.03928:
        return c_ / 12.92
    else:
        return pow((c_ + 0.055) / 1.055, 2.4)


def luminance(c: RGB) -> float:
    r, g, b = c
    return 0.2126 * sRGB(r) + 0.7152 * sRGB(g) + 0.0722 * sRGB(b)


def contrast(fg: RGB, bg: RGB) -> float:
    fg_l = luminance(fg)
    bg_l = luminance(bg)
    return (max(fg_l, bg_l) + 0.05) / (min(fg_l, bg_l) + 0.05)


def accent(c: RGB) -> RGB:
    on_white = contrast(c, (255, 255, 255))
    on_black = contrast(c, (0, 0, 0))

    if on_white > on_black:
        return (0xFF, 0xFF, 0xFF)
    else:
        return (0x00, 0x00, 0x00)


def hex_to_rgb(h: str) -> RGB:
    return int(h[0:2], 16), int(h[2:4], 16), int(h[4:6], 16)


def from_apple_colorset(path: str) -> RGBA:
    with open(path) as f:
        colorset: dict[str, Any] = json.load(f)
        components = colorset["colors"][0]["color"]["components"]
        return (
            int(components["red"], 16),
            int(components["green"], 16),
            int(components["blue"], 16),
            int(float(components["alpha"]) * 255),
        )


paths = [
    ".../Color.colorset/Contents.json"
]

white: list[str] = []
black: list[str] = []


for path in paths:
    color_name = path.rsplit("/", 2)[-2].split(".")[0]
    if " " in color_name:
        first, second = color_name.split()
        color_name = first.lower() + second
    else:
        color_name = color_name.lower()

    color = from_apple_colorset(path)
    a = accent(color[0:3])
    if a == (0, 0, 0):
        black.append(color_name)
    else:
        white.append(color_name)

print(f"case {", ".join(("." + b for b in black))}: .black")
print(f"case {", ".join(("." + w for w in white))}: .white")