I am currently in the process of trying to cut part of a circle while still displaying the full image that is masked. It might be easier to show an example.
I am trying to do something like this:
This is what I have:
But I'm not really sure how to get that same effect.
You can add a border to the image.
To add a border to a masked image: Select the mask from the layers in the left side bar to show the "Borders" section in the right sidebar.