Luminance Converter

# Luminance unit conversions (base unit: cd/m²)
LUMINANCE_TO_CD_M2 = {
    "cd/m2": 1,
    "nit":   1,            # 1 nit = 1 cd/m²
    "fL":    3.42625,      # foot-lambert
    "sb":    10000,        # stilb
    "asb":   1 / 3.14159, # apostilb
    "L":     10000 / 3.14159,  # lambert
    "mL":    10 / 3.14159,     # millilambert
    "skot":  1e-3 / 3.14159,   # skot
}

def convert_luminance(value: float, from_unit: str, to_unit: str) -> float:
    cd_m2 = value * LUMINANCE_TO_CD_M2[from_unit]
    return cd_m2 / LUMINANCE_TO_CD_M2[to_unit]

# Examples
print(f"1 fL = {convert_luminance(1, 'fL', 'cd/m2'):.4f} cd/m²")
print(f"1 sb = {convert_luminance(1, 'sb', 'cd/m2'):.0f} cd/m²")
print(f"300 nit = {convert_luminance(300, 'nit', 'fL'):.2f} fL")