I go through my photo collection and place face tags manually. When I find picture without any detected face but with actual faces I want to add face tags to picture and to fill tag names.
Is it possible to force face detection and/or face recognition to just a single photo? Possibly with shortcut.
Yes. DigiKam will do face recognition of a single photograph so long as you have other ones of the same face with tags to use for reference.
The KDE UserBase Wiki outlines the technique and procedure in several languages. You can find their relevant info here:Digikam/Face Recognition
Picasa by google used to do this very well. after you have tagged a few people it then asks you to tag images where it cant recognise the people. it doesnt take long for it to be able to scan your entire directory and find everyone. you can then search for photos containing person a+b but not C for example.
I know this has been 'retired' as a program by google, and replaced. However for the face detection alone if this is something you need. Like finding every photo of a certain person, it may be worth downloading anyway.
