husl_error_test.py

from mpmath import mp, sqrt, atan2

mp.dps = 250

luv_good = mp.mpf("36.14585083971970000000000000000000"), mp.mpf("0.00000000000179982851973451000000"), mp.mpf("0.00000000000059994283991150500000")
luv_bad = mp.mpf("36.14585083971970000000000000000000"), mp.mpf("0.00000000000178678628408426000000"), mp.mpf("0.00000000000062602731121200500000")

lch_good = mp.mpf("36.14585083971970000000000000000000"), mp.mpf("0.00000000000189718584003013000000"), mp.mpf("18.43494882292200000000000000000000")
lch_bad = mp.mpf("36.14585083971970000000000000000000"), mp.mpf("0.00000000000189328165347235000000"), mp.mpf("19.30867293488920000000000000000000")

def sub(a, b):
    for x, y in zip(a, b):
        print "    ", x - y

def convert(L, U, V):
    iss = [L, U, V]
    iss.append(U * U)
    iss.append(V * V)
    C = sqrt(iss[-2] + iss[-1])
    iss.append(C)
    Hrad = atan2(V, U)
    iss.append(Hrad)

    H = Hrad * mp.mpf("180.0")
    iss.append(H)
    H = H / mp.mpf("3.1415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091")
    iss.append(H)

    if H < mp.mpf("0"):
        H = mp.mpf("360") + H
        iss.append(H)

    return (L, C, H), iss

lch_result_good, iss_g = convert(*luv_good)
lch_result_bad, iss_b = convert(*luv_bad)

print "good deltas: "
sub(lch_result_good, lch_good)
print "bad deltas: "
sub(lch_result_bad, lch_bad)
print "algo deltas: "
sub(iss_g, iss_b)