In reply to a comment that said nothing about projections, you wrote:

> You can certainly apply projections to images, I mean this is what photoshop does.

What's the relationship of this to anything in the comment you replied to?

"You would never matrix multiply an image onto another vector."

> "You would never matrix multiply an image onto another vector."

That wasn't me. But I can still elaborate: while you can certainly consider a non-color image as a matrix, the operation of multiplying this matrix with a vector is rather meaningless.

While a lot of things can be made into or viewed as matrices, a matrix is typically only meaningful as a representation of a linear map.