I think it doesn't matter if you market well and make it easy, people do want things that make their live easier and in a very small way this is one of those.
I built a thing to resize app icons/screenshots years ago and it still gets thousands of visitors per week: https://apetools.webprofusion.com/ - I didn't get around to monetizing it though!
I'm also not sure if this is the only effect the app can do.