Absolutely. With the setfield command we are setting the value for the field _canonical_uri, text, and moved. _canonical_uri is a default field that tiddlywiki looks for that marks the tiddler as a placeholder pointing to a specific address. text is a default field containing the text of the tiddler. moved is a user created field we use to mark the tiddler as having been run through the script already so that tiddlywiki doesn't overwrite the moved image with the empty file we create with the script. Ie if we didn't mark the image tiddlywiki would move the empty placeholder and overwrite the actual image on a second pass.
the setfield command looks for the field to set and then requires a tiddler with the value of the field as it's text. so
the tiddler ..../empty_text is just an empty tiddler. Therefore the text of the placeholder tiddler is set to empty. You may have to use a space I can't remember.
the tiddler ..../moved_field has the text 'yes'. therefore a field called move is created on that tiddler and it's value is set to yes. now on subsequent passes of the script tiddly wiki will ignore this tiddler and only act on those images ( is[image] ) that do not have the value of yes ( !moved[yes] )
the tiddler ..../canonical-uri-external-image has the value of the _canonical_uri and generally requires some sort of transclusion of the tiddler title so that it is unique. In my case is:
./images/<$view field="created" format="date" template="YYYY"/>/<$view field="created" format="date" template="0MM"/>/<$view field="title"/>
This points to the directory that I saved to in the first line by adding the images/month/year to the filename of the actual image so that tiddlywiki moves it to that directory.
Hopefully that makes sense please feel free to ask.