[digiKam-users] face tagging persistently ignore a face

[Thomas]

On 2023-03-02 17:58, Travis Kelley wrote:
> 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.
>
>

While I can see arguments for doing it this way, I don't think it is a 
safe assumption that an image will be scanned only once. This assumes 
that the face detection does not improve over time. Let's say you have 
photos that includes N people. You run face detection and DK detects M 
regions with faces. Now M will likely contain some percentage of N less 
than 100 %. Plus some regions that are mis-detections, ie. face detected 
when there is none.

Then time goes by. A new version of DK is released with a better face 
detection. Now you would want to re-run face detection and include 
already scanned images, right? How else would you be able to detect all 
the ones that were missed on the first run?


Now if you have a few hundred photos that will likely not be a problem. 
But when you have thousands or hundreds of thousands of photos, the 
amount of mis-detections is huge.

Hopefully, future versions of DK will save a region that was detected as 
a face but marked by user as being not a face. I think it should save 
that region in the DB with a note that this region should be ignored.


Note: a single photo may contains dusins of mis-detected "faces". 
Especially if you have high resolution pictures of high entropy stuff 
like sand, dirt, gravel, concrete, shrubbery, etc.



-- 

Mvh
Thomas