[digiKam-users] face tagging persistently ignore a face

Travis Kelley rhatguy at gmail.com
Thu Mar 2 16:58:26 GMT 2023

Let me caveat this by saying I'm not an expert/developer, so I'm only
commenting on what I've seen.

When you use the red X button it throws away that detected region
completely.  It doesn't save anything to the metadata of the photo.  I
don't believe anything gets saved in the database either (more on that
below).  It's as if that "detection" never happened.

My understanding of the intention of detection is that you should only need
to run it on a photo once.  Hence there is a setting under detection to
only scan NEW photos.  You are not prevented from rescanning a photo, but I
believe the normal workflow would not be to do that.  Hence using the red X
button effectively makes it as if the detection never happened and unless
you specifically rescan a previously scanned photo, that same region would
not get detected again.

Adding blurry face regions to the "ignored" tag will cause other things to
match those later.  I've seen real people that appear in multiple photos
get "matched/recognized" against a name of "ignored" because they were
ignored in previous runs.  You need to be somewhat careful in what you
ignore as if you ignore someone important there is a chance the next photo
of that person will be "recognized" as the "ignored" person.  You can
always correct that match and tell digikam that person is a real name if
that happens.  From everything I can tell, "ignored" is not treated as a
special tag at all.  It effectively creates a name of "ignored" that gets
treated just like any other person name.  It gets written to photo metadata
and I can for instance look at all the people named ignored in PiGallery2
(which reads the face metadata that digikam created).  I suppose it would
be fairly easy to strip all of those out at any time by deleting the
"ignored" name in digikam or using something like exiftool, but they
haven't caused me to much trouble other than philosophically the creation
of useless metadata.

Someone with more knowledge feel free to correct me.  I'm only going based
on experience having used digikam for a while.

On Thu, Mar 2, 2023 at 7:08 AM Thomas <sdktda at gmail.com> wrote:

> On 2023-03-02 13:00, Travis Kelley wrote:
> > Yes.  When you "ignore" a face, you are essentially marking that face
> > with a name of "ignore".  Other software will see the tag in the
> > metadata of that photo.
> Does this mean that it is problematic to tag exceptionally blurry faces
> as "ignore" in that this could result in some kind of "catch all face"
> that will match a lot of faces incorrectly?
> PS. What about the "This is not a face" (red X button) - does this also
> just tag the detected face region as a "not face" tag? Or does it rather
> just throw the face out of the detected faces pile (thus, resulting in
> this image region being re-detected as a face some later time)? Or how
> does this work?
> I have noticed that when I have a picture with high entropy regions like
> a heap of gravel or rocks, it will often detect faces in that "noise". I
> always click "This is not a face" but I have a feeling that the same
> regions keep turning up when I do face detection again. But maybe it is
> just other regions of the same "noise"?
> --
> Mvh
> Thomas
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