From what I understand, there was a feature to add custom thumbnails for media files in previous versions of Webtrees, which was removed in 2017. While I understand the reasoning behind it, I still miss the option to add preview images for non-image media like documents and videos. Wouldn't it be possible to add another media file to the media file, flagged as "type: thumbnail" or "type: preview image"? This way, we could still have different resolutions and a GEDCOM-compatible way to import and export those thumbnails.
This feature has been converted into a "GEDCOM-compatible" system.
GEDCOM allows a media object to contain more than one media file.
What you need to do is add a second media file containing the image.
webtrees will use the first image file in a media object for display.
So if you have a media object containing a video and an image, then the image thumbnail will be shown.
There is an option in the control panel called "Import custom thumbnails from webtrees version 1"
We don't know if the existing thumbnails were created automatically by webtrees - or were created by the admin.
So, it will show you all your existing thumbnails side-by-side with the main image, and give you links to either import them into the existing media object or delete them.
It's much simpler than it sounds.
> So if you have a media object containing a video and an image, then the image thumbnail will be shown.
Hm. I just tried it (uploaded the video and a preview image in the same media object), and that's the result:
Both the thumbnail and the placeholder icon are shown (including the title and filenames of both), and clicking on the thumbnail only opens the thumbnail - not the video. :-/ I would have expected to see the preview image only, and clicking it would open the video, no?
Same in the media object list:
The preview image does not replace the icon, but is shown additionally, and clicking on this preview image will not open the video.