[gentoo-user] imagemagick display image edit tool draws an opaque background

[n952162]

In all of the imagemagick display installations I have, when I use the
image edit draw function, it includes an opaque background, rather than
just the lines themselves.  I've never had this with display(1) before,
and can find nothing in the internet about it.  That suggests to me that
it's - again - a use-flag issue.  Is there some use flag I have to use
to have a colored line with a transparent background?