Clamp A UI image to an irregular shape.

So ive been trying to sort this out for the past couple of hours and i figured i would ask for some assistance. i have created a minimap that works well, initially it was a circle and i had the icons claping to the circumfrence. But after a while i decided i wanted a difference shape and settled on a hexagon.

Obviously the question i am asking is how would one go about clamping an icon on the UI to a hexagon shape?