Which is usually png and browsers can read that,
but they can't read our internal metafile format (svm)

Change-Id: Idfd82da630ead69f508b74285081e32315030825
Reviewed-on: https://gerrit.libreoffice.org/45590Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Samuel Mehrbrodt <Samuel.Mehrbrodt@cib.de>
Reviewed-on: https://gerrit.libreoffice.org/45679