VERY SIMPLE
Your program is the only one that I have ever work with that does NOT save your work.
I'm using it on my Samsung View and after importing and image and working on it, then Saving it all it does is save the unworked image and I works when it wantstill to so Saving is random sometime it works, 90 percent of the time it doesn't.
So make it simple.
Have an option where you want to save it as well as the option to share.
Saving to gallery is the same, works when it want to.
Or if that's a problem just have a button to take a screenshot of your work because that's the only way to save my work.