There is a software (I suppose there are more) under Windows, which claims to take high quality frameshots from videos, called Moment
I suppose it works in a way that it takes a set of consecutive frames from the video and merges them with some algorithm. I am looking for similar software under Linux, that would work from command line.
If you can recommend me algorithms only, that's fine as well, I can try implementing and using other software to grab the frames (eg. ffmpeg).