The `updateImageId.py allows you to update a static iiif implementation to be severed from a different directory. To add a prefix to an existing Id run:
./standalone-iiif/updateImageId.py json_file 'https://glenrobson.github.io/iiif/welsh_book/
where https://glenrobson.github.io/iiif/welsh_book/
is the prefix to insert.
To replace part of the prefix run the command as follows:
./standalone-iiif/updateImageId.py json_file 'to_replace' 'https://glenrobson.github.io/iiif/welsh_book/