However, I'm not really sure that would work, since I don't think that would be able to bypass iOS prompting you to give that app access to your photo library.
There's a third-party "ScreenShieldKit" which claims to be able to do this:
So, apparently it's technically possible to block this, but AFAIK, Apple doesn't provide an equivalent to Android's FLAG_SECURE ("treat the content of the window as secure, preventing it from appearing in screenshots or from being viewed on non-secure displays").
DRM-protected video can't be recorded (or screenshotted) in iOS, but as another comment noted, that seems to be a video-specific thing.
