OptionalImageBinaryFunction
class OptionalImageBinaryFunction<A, OA : ObservableValue<A>, B, OB : ObservableValue<B>>(argA: OA, argB: OB, lambda: (A, B) -> Image?) : BinaryFunction<Image?, A, OA, B, OB> , ObservableOptionalImage
Boilerplate which avoids having to use generics.
Similar to ImageBinaryFunction, but the value can also be null.