delta E76
Takes two CIELAB values and calculates color difference (dE) using CIE1976 formula. NOTE: both CIELAB values must share the same reference white. If they do not: convert to XYZ, adapt, convert back to CIELAB before calculating dE
Return
delta E (1976) value
Parameters
lab1
First CIELAB value (element order L, a, b)
lab2
Second CIELAB value (element order L, a, b)