What does the rebus mean? The rebus is as follows: It is very necessary.
It could be a
One meaning of self is I and selfless is opposite of selfishness and it is very necessary.
It is obviously
Brainy Smurf (Schtroumpf à Lunettes in the original french version).
This is a king missing an I (or an eye). And as we know it : in the land of the blind, the one-eyed man is king.
So, this is a kingdom full of blind people. Also, the king is blue. The only logical explanation is that this is the Smurf village where all Smurfs went blind (because of some Gargamel's trick or whatever). And which Smurf managed to keep at least an eye in working condition ? The one wearing eye-protection of course. Glasses.
Hence : Brainy Smurf.
A possible answer is:
A just king.
A just king with perspective.
The king has no "i" (or "no eye") and as justice is blind, so is the king —a just king. And there is the possible addition of the word "perspective" as the letters are shown at a perspective angle. And I would say "It is very necessary" for a king to be just and have perspective.
Another possible variant:
A king with a just perspective.
My 1st answer: it means
It's King divided by $i$, the imaginary unit. So, a real number is left.
Elvis has left the blued i in "ing"
"The King" has left out the expected blue-outlined "i" in the "ing" part
Because there is no 'I', which pronounciation is similar to 'eye'.