I didn't have any problem with a screenshot I took and pasted into a Google Doc.
After sanitizing the clipboard – I was able to select it, and copy it back out.
I could easily paste into Jedit X, Jedit Ω, Pages, Word 2011, Apple Mail.
This is on macOS 10.12.6 Sierra.
I tried first with Google Chrome, but following up with Safari worked equally fine.
I could NOT get Preview.app to work with the clipboard image, nor could I get Keyboard Maestro to write it to a file without pasting to Mail (or another app) and copying back out.
So this would appear to be doable without any major hoop jumping.
thanks @ccstone , will try again.
Hadn't thought about pasting the image into other programs and see if that worked. Will try that as well
Edit:
Tried again, now this time with another image and it worked... but just for this 2nd image. Both images are in the same document, both are same filetype, both came from the same source as well... ...
Went back to the 1st image and it still doesn't work...
Maybe there's some change of format somewhere?
Remembered Office, specially Excel transformed some images (WMF?), that used to mess up with the images.
Maybe Google is doing the same?
Anyway, thanks CC, will check them manually for now.
Appreciate having looked at this