Currently Sprite assumes that all its work happens under a "public" directory, and that "public" directory is published at "/".

That's not the case for me -- I'm working in a Java environment with a layout like the following:

static-ui/
src/
main/webapp/
images/
style/
target/
webapp/ # published as /static-ui/
images/ # published as /static-ui/images/
style/

I'd like to generate URLs like "/static-ui/images/mysprite.png", or even "http://images.example.com/mysprite.png"

(I'm fixing this in my own fork, but leaving this ticket as a record and for discussion)