No special way, since I don’t know dokuwiki much:
- batch download of original images with DownThemAll! Firefox add-on
- Images manually renamed to something meaningful.
- Upload to Dokuwiki (supports batch upload).
If you have access to the code of original posts (markdown…), I think it would be even easier:
- copy code to a file
- Use an editor with “search & replace” (or a
sedlike tool) to add the domain to the image’s urls (to make them absolute instead of relative).
- use pandoc (command-line) to convert markdown to dokuwiki (or just use search & replace in the preceding step to add the opening and closing tags for dokuwiki images)
- Paste it into dokuwiki.
In the latter way dokuwiki should cache the external images. But the images names would be gibberish.