One of the four core-metrics of the Wikiloves tool suite, as documented in Tool:Wikiloves#Metrics is “Images used in the wikis How many of these uploads are in use in the wikis”.
This is achieved by checking whether the image is in the gil_to column in the globalimagelinks table (code).
This method will obviously considers all usages as equal, including transclusions in the Wikipedia: or Project: namespaces. If a competition would, for example, build in the Wikipedia: namespace galleries of all pictures uploaded (per monument/location/uploader/etc.), then this would lead to ~100% usage, which might be surprising.
- Should the query discriminate on namespace when calculating the usage?
- Which namespace should be used?
Some relevant previous work:
- Glamorous will offer a tickbox “Namespaces − Show file usage in article namespace only”
- Baglama will consider all namespaces
(Per its design, the wikiloves tool cannot make it a user-selected option.)