Simple algorithm : https://www.72.sk/menu.php?m=RGA

So, we introduce the degree of additivity (with an approximate relationship), Adt :

Adt = 0.2220×Delta − 0.0875×Avg + 0.0235×Max where : Delta = ABS(a1 - a2) Avg = (a1 + a2) / 2 Max = MAX(a1, a2)

Thus, the mixture of two colors, a = a1 + a2, can be calculated as follows:

a ≈ Adt(a1, a2) + Avg(a1, a2) This result must of course be in the interval a1, a2.