File Download server action

Can I use the File Download server action with an image file.

My action file, loads an image, resizes it, adds a watermark, and saves the output to a folder, each time i add the File Download step at the end of that, it just does nothing, like it completely ignores the step. If I change the path of the download to something I know is incorrect, then it does error out with a 500 file not found error though.

If it makes any difference, I am using docker with digital ocean and the download is coming from the user uploads folder.