not the creator but
I have a question for the creator here... sort of a feature request.
You're already using separate image maps for each type you can attach to the world_gen file, like Volcanism, Drainage, etc, right? So what about being able to import and export these images as well as the height map. That way we could import, say... a Volcanism map that specifies exactly what and where we want the volcanism, instead of playing around with noise and whatnot.
While this would be a cool feature, I have to ask... you know about the paintbrush, right?
Also, as sort of a tecnhical question, not necessarily towards the OP, what resolution is the map imported into DF as? If I have a 256x256 map, does that mean that Perfect world is feeding DF a 256x256 image as a height map? Because the image that you get exported from legends in worldgen is something like 16x that size. Is it at all possible to somehow edit THAT map at THAT resolution? Because I'd love to be able to set up a world where the rivers didn't all have canyon walls. Or maybe not have rivers that cut through a sheer cliff face because they can't run up-hill... I can do better terrain generation than DF does with freaking PAINT!
I think I can answer this, too. If you look into the post-import world_gen.txt file, you can see PW's output. If you zoom way out, parts of it actually look kind of like an ASCII map, but whatever it is it's all text which means it's amazing it can even pull off 256x256--that's over 60,000 tiles, each with several dimensions. DF then uses that data to procedurally generate a far more minutely detailed playable world-map (at least down to individual embark tiles, 256 per world-gen tile); that's what the legends export is drawing from.
Regardless, it's all built off the output for the in-application worldmap painter (which a lot of people don't even know about because it's a terrible PW buried in menus), so I'm pretty sure there's not much cephalo can do to change the resolution.