It seems that libre/open office doesn't support this option. Only way is to remove and again insert embedded image, but you must be aware of formating (e.g. size etc.). I achieved my goal by doing these steps (WARN it is hack...):
- Save HTML to odt. In this odt graphics are linked to files on disk.
- Unzip odt file.
- Create directory
Pictures
in unzipped directory and move there all images. - Edit
content.xml
and replace path to system files toPictures/file-name
. - Edit
META-INF/manifest.xml
and something like this<manifest:file-entry manifest:media-type="image/png" manifest:full-path="Pictures/file-name"/>
- Zip folder and change extension to odt.
- Read odt file via Libre/Open Office Java Uno API. Now this document has embedded graphic objects.