Honest question: If you take a copyrighted photograph and convert it to geometric shapes, how “blocky” does the picture have to be before it’s no longer a copyrighted work of the original artist?

I mean, if it’s almost identical with a huge amount of shapes, I can understand that it’s reasonable to look at it as the same piece of work, but on the other hand if you make it blocky enough that it looks like an interpretation of the original image as a new work in its own right, what ownership does the original author have? None, some, complete?