prlpz wrote:

Furthermore, the names mentioned in PDF should be authors of images cited in the way required by the license of each image.

It is impossible to solve this until you have a way to tell which edits are substantial and which are purely technical. The same applies to the textual content. We only have a "minor edit" flag.

Sometimes the original uploader is not the most important contributor, as somebody might have uploaded an improved version of the image (for example something was broken in the original file).

Actually we should use Extension:CommonsMetadata for this if enabled.

prlpz wrote:

There are some ways to tell, or, at least, to tell better than now:

• People who have not uploaded any version of the file aren't the authors of the file. In the examples provided, there was only one version of the file, uploaded by one user, who obviously was the author. People who didn't upload anything aren't file authors, even if they edited file description page.

• Some license templates provide the requested way to credit the image. I expect most of those templates to be machine readable.

It is also possible to be the only uploader and not the author e.g. in the Flickr imports...