[jerf]

No free lunches. For a lossless compressor, (Information theory bits of polygons) + (Information theory bits of remaining error) >= (Information theory bits of original image), where the > represents the possibility that the first two elements aren't perfectly separated by your process or have inescapable overlap.

I specify "information theory bits" because they aren't really what you see in the computer's RAM; they're closer to "post-compression bits". But regardless, no matter how you move the encoding around there is no escaping information theory.

[moultano]

Obviously. That's the definition of compression. If the image is well modeled by overlapping polygons + small residuals, the encoding will better approach the uncomputable ideal, and thus, compress.