Oh OK it does work if you try - I didn't try hard enough.
See
http://www.contextfreeart.org/mediawiki ... er:Kipling for what was confusing me. Are the trailing ?n numbers the version numbers (such as when the image is uploaded). If so, does omitting them (as seems to be necessary) give the first or last version?
Before I put together a wiki template to automatically import the thumbnail of a gallery design, it would be nice to know if the thumbnails have URLs other than those that appear in the gallery pages. Looking at these, it seems that you have them at
uploads/x/y/hash/sm_thumb_nnnn.png
where "hash" is unique to the author (hash of name or user id, I guess), and x and y are the first two bytes of this hash.
The problem is that the wiki template will have to have the x/y/hash as a parameter, or the whole URL. It would be much cleaner if there were alternative URLs like
http://contextfree.org/gallery/thumb/nnnn.png (either as static files or via a PHP script that does this on the fly). Then I could write a wiki template that say took {{gallerythumb|id=1828|title=ammonite|author=bloop}} to create a nice little captioned thumbnail linked to the gallery. Otherwise I will also have to have, for example
url=
http://www.contextfreeart.org/gallery/u ... b_1828.jpg
or
dir=4a/ca/4aca29c7c0a76c1cbaad40b2693e6bef
both of which would require the wiki author to looking up the thumbnail image URL, trim off the "?1", etc.