cause we have a shared_ptr to it at this point, so its never unique,
so a new copy is always generated.

this really peaks memory with large images.

Change-Id: I53dab2a1f6e5102b9af08dd6365187a383f7c247
Reviewed-on: https://gerrit.libreoffice.org/35003Tested-by: Jenkins <ci@libreoffice.org>
Reviewed-by: Caolán McNamara <caolanm@redhat.com>
Tested-by: Caolán McNamara <caolanm@redhat.com>