dnd 5e – Does Silent Image provide cover?

Let’s say we’re trying to give a Giant Ape three-quarters cover from a distant archer. A spellcaster casts Silent Image to place a rock in between them of the right shape and size to cover 3/4 of the Giant Ape in that direction.

Does the archer shooting the Giant Ape have to overcome +5 AC from cover? Or does the fact that the illusion is permeable by arrows result in no additional AC?