Adjusting IQ balance for audio sources

I’m wondering what block GnuRadio offers to adjust IQ balance to
maximize image rejection from an audio source. Is there a block
available, or a description of a (perhaps manual) algorithm I can
implement with existing blocks?

I’ve attached something that I used a while back to manually adjust I/Q
balance.

Also, the gr-osmosdr folks have an automatic IQ corrector “add on”:

See this mailing list discussion:

https://lists.gnu.org/archive/html/discuss-gnuradio/2013-03/msg00245.html