From webclient, using General > Download > Export as OME-TIFF, one can generate a OME-TIFF file on the server and then download it. Using command line tools etc, one can then extract the embedded OME-XML metadata.
I wonder if there is a way to directly extract OME-XML from an image in OMERO using Java API. But I could not find relevant Java class in API. Is there any way to achieve this by programming?