Ok. So here's the latest version then. I haven't included your lightsourced brushes yet CM. I'm not really sure what you meant in your earlier post about changing the directory names. The brushes I made the default ones DO have shading images with them. And shadows.
Anyway... here it is. Let me know how you get on with it. If you load your alpha BEFORE you add the jitter then you may need to press generate to have any trees out of the confines deleted. Oh and btw, I forgot to mention earlier, the program offsets the trees so that they should be positioned from the base of the trunk. So the trees will stick out at the top but there shouldn't be any trunks outside the area.
The sourcecode is also uploaded for Fluesopp to pick apart and for anyone with a mind to see if they can spot how many memory leaks there are and how much garbage is generated every time a button is pressed.