Adding a stroke around a matte control

I have a mask that I am choking back with a MatteControl. is there a way to put a stroke/line/outline around that?

outline-around-mask.png (141.41 KiB) Viewed 1793 times

Imagine putting a red line around the white version. How would you outline that?

Try to pipe your image in a Erode / Dilate node, expand it, colorize it red, and merge it behind your original image

That worked great. Thanks.

jello-outline.png (155.07 KiB) Viewed 1772 times