how exactly would you search for the specific feature I proposed? There's hundreds of image apps out there, I doubt there's one that specifically says it does that in the headline.
Another approach is to discuss your idea with as many people as possible. Maybe you haven't heard of such an app but someone else has. This should be most fruitful if you do this with your target audience. Even if there is such an app out there but your target audience hasn't heard of it, then that's a good enough reason to try building it.
But you're right, that's a good way to think about it.