i was kinda surprised that a photoshop (or illustrator?) filter that did this doesnt exist. maybe it does. i guess the tricky/weird part of it is that it combines both raster (photoshop) and vector (illustrator) functionality.
although, i suppose in photoshop you could do it by making paths out of the shapes, then export those paths as illustrator. the long-term goal was to have an arbitrary vector-based shape (like, say, a vector letter, or a star, etc) that filled the shape in.
it takes a long time to run, otherwise i might make a web page where you could upload images and get the output pdf. (also, you have to manually break up [color separate] the original image, so there is a lot of manual work now. would be nice if i could automate that part, which i could, in theory...)