twotone is a command-line tool that will take a PNG and generate a flattened one
with the given background and foreground colors.
By default it will leave background transparent.
go get -u github.com/kytrinyx/twotone
export TAN=EAE0CC
export BROWN=2D232A
twotone -bg=$TAN -fg=$BROWN -in=fixtures/test.png -out=fixtures/out.png
no smoothing of edges
That probably has a name, but I'm not a graphics person. If I need it I'll probably spend a few minutes (OK, hours. Whatevs!) figuring out the fix for it. So far I've been lucky: when I resize it in Keynote.app, it smoothes the edges for me.