Generate background colors for strings that will be displayed with white text

synesthesia.py

import colorsys

FNV_OFFSET = 0x811C9DC5  # 2166136261, FNV-1 32-bit offset basis
FNV_PRIME = 0x01000193  # FNV-1a 32-bit prime


def fnv1a_32(value: str) -> int:
    """
    Compute the FNV-1a (32-bit) hash of a given data string.
    https://en.wikipedia.org/wiki/Fowler–Noll–Vo_hash_function
    """
    output = FNV_OFFSET
    for v in value:
        output ^= ord(v)
        output *= FNV_PRIME
        output &= 0xFFFFFFFF  # Use 32-bit arithmetic
    return output


def to_hsl(v: int) -> tuple[int, int, int]:
    # Extract HSL components from the integer hash value
    return (v >> 20) & 0xFF, (v >> 12) & 0xFF, (v >> 4) & 0xFF


def background_color(value: str) -> str:
    """
    Returns an RGB hex code for the string, which is usable as a background color when using white text.
    """
    h, s, l = to_hsl(fnv1a_32(value))
    r, g, b = colorsys.hls_to_rgb(h / 255, (l / 255) * 0.3 + 0.2, s / 255)
    return f"#{int(r*255):02x}{int(g*255):02x}{int(b*255):02x}"