Comment by sitkack

That is cool, but we cant be guaranteed that will always be the case, nor could we make a statement about all phones, it would be a phone by phone basis. Esp on Android where someone could have an alternative screenshot application.

Depending on your threat model, I'd argue that it would be impossible to prove that metadata is not included within the image itself (alpha channel, noise, pushed pixels, colorspace skew, etc).

I'd be interested in stego techniques that can survive image reduction and denoising.