Decoding the image-data from a notification

I've had `dbus-monitor "interface='org.freedesktop.Notifications'"`
running as a service, so the data from notifications is saved in the
journal.  How could I turn the `image-data` array of bytes back into an
image?  Right now I only have a couple entries I'm interested in, so
something crude and manual is fine as long as I get a viewable PNG or
JPG or whatever back, then I can work on something more automated that
is perhaps also running in the background and saving the image-data as
it arrives.  Thanks