I see - this isn't really a linking query. The image will always technically exist on a different page to your app if it's called via iframe, as an iframe is simply a window that displays a different web page within another.
A way around this might be to use canonical URLs, but Google seems conflicted as to whether images can use these:
https://webmasters.googleblog.com/2011/ ... aders.html
I don't know off the top of my head if Google differentiate between page and image headers; for this purpose I wouldn't imagine so.
So the last option would be some .htaccess wizardy:
https://stackoverflow.com/questions/767 ... e-redirect
http://forum.coppermine-gallery.net/ind ... ic=76683.0
https://www.reddit.com/r/SEO/comments/2 ... s_results/
I've never personally used any of techniques, but they seem doable