We're starting to integrate text extraction for djvu and pdf files -- currently used for ProofreadPage extension -- but it's not currently exposed to the search indexing.
This is also something frequently desired for text document types like .doc and .odf, and there are some extensions for doing that but there's not a clean interface to plug it in to that can be supported for all search backends.
Note that supporting the Lucene search which updates separately might require some additional attention.
- bug 6421 - search djvu file text
- bug 6422 - search pdf file text
- bug 13370 - search file metadata
Also interesting idea:
- bug 18045 - search text of linked files (but if these are remote, that's much harder to handle!)
Things we need:
- clear interface on File for things that need to be fetched (exif metadata, page text)
- clear interface on the SearchEngine class for plugging additional info in to updates
- a way to expose additional searchable info to the Lucene search's updaters (plugin to oai interface maybe to toss in extra data fields?)