a suggestion for you: would it be possible to implement a size feature?

for example, on me Darklands map, the default sized tree brushes (~30px) were way too large, but when dropped to 1/3 (~10px) they were perfect. Or would it be too hard to program in? I suppose one alternative would be to take your masked area, triple it in size, and save that as the png, then shrink it when it's done.

Also, another suggestion would be a way to increase/decrease density (more scattered trees, or more overlapping etc).

Wish I could program so I could help on this.. (and this is in no way trying to slight your work, just giving you feedback as a potential user as to the things that would be useful features to me). Repworthy, for sure!