The "opposite" to multiply mode.
Both parameters are inverted, multiplied by each other, the result is inverted again.
This returns a brighter result
than both input parameters in most cases (except one of them equals 0).
Completely black layers do not change the background at all (and vice versa) -
completely white layers give a white result.
The average of multiply and screen mode is exactly the average mode.
f(a,b) = 1 - (1-a) * (1-b)
This mode is commutative (base and blend color can be swapped).