At this time, there is unfortunately no way to bulk upload alternative reference images and thumbnails. They are automatically generated from the master digital object. You can manually delete the derivatives and upload your own, but right now it's a one-at-a-time process via the user interface.
I suspect you know the following, but for other users encountering this post, I wanted to add a couple of clarifications as well:
You mentioned that "it is possible to attach multiple digital objects to a given information object." In fact, this is not the case.
AtoM maintains a 1:1 relationship between a digital object and an information object (AKA an archival description). When you use the "Upload multiple digital objects" option, you are actually creating new lower-level descriptions beneath the target description (one per digital object), and then attaching your digital objects to these new records (aka information objects). I've outlined this in detail in previous messages such as this one
, but I just wanted to be sure to reiterate it. There is no way to directly attach multiple digital objects to the same description.
Second, the way you are using the digital object module *can* work, but I want to make sure you're aware that this is not how it is intended to be used.
When linking to an external digital object, AtoM expects that the URL provided meets the following criteria:
- It is prefixed by http:// or https:// - FTP links will not work, nor will links to attached network storage/alternative drives on a local computer, etc.
- It is publicly accessible on the web - not behind any firewalls or requiring passwords to access, etc.
- The URL ends in the file extension of the digital object - that is, it is a link DIRECTLY to the digital object, and not a landing page on which the object is found
It is this last point, #3, that you are encountering, and why you are getting a blank generic icon for your PDF. It sounds like you are pointing to a landing page on which the PDF is found, rather than to the PDF itself. I understand that you may be doing this intentionally, but just wanted to make sure it's clear to other users that this particular workflow is not officially supported. Because of this, we don't currently have a method to bulk alter the thumbnails or reference display images in the way you've inquired about.
So for now, if you want to continue with this approach, you'll have to manually alter the thumbnail and reference image for each upload. Anything else would require analysis and development to implement. If your institution is interested in potentially sponsoring such work, please feel free to contact me off-list.
PS - in case you are following this approach because all of your PDFs have the same cover page and you want more diversity in the display images - there's actually a setting that can do this for you!
For PDFs, you can set a different page as the one used to generate the derivatives. See: