I have trouble understanding something (small) regarding the math behind Harris Corners Detector.
(for example I looked at this explanation - https://aishack.in/tutorials/harris-corner-detector/)

In the equation we get there are squared derivative matrices - Ix^2, Iy^2 and also Ix*Iy. I've seen code implementations of this around the web, and it seems to me that these multiplications are element-wise.
My question why? I thought that when you take the square of a matrix it should be matrix multiplication, and not element-wise multiplication...

I'd really appreciate some clarifications regarding this,
Thank you