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Should be feasible to add these to Mapnik's supported comp-op list (compositing operations):
some progress c1c5421
add linear-burn, linear-dodge, and divide comp-ops - refs mapnik/mapn…
…ik#1448 and mapnik/mapnik#1432
finish python bindings + tests for #1448 and #1432
@artemp - excellent, visual results do look different than the normal color-burn/color-dodge and I've added them in 2b1ab49.
good work, guys!