How to make the area around an image transparent with Paint.net

Grunt's Ghosts

I've been looking for this one Google all day but nothing shows me how to do this without making a different layer each time which will take forever. Basically, I want to copy some tree sprites I have and copy/paste a ton of them on my map but I have a problem of a colorless boarder keeps cutting off already placed trees. I'd like to make it where I can place trees slightly over trees to make it look like a dense forest but I'm not sure how to keep that colorless boarder from screwing things up.

HELP!

Prime

Pretty easy if you have a steady hand

Lasso select (from the toolbox) what you want to keep.
In the menu go Edit -> Invert Selection
Hit the delete key

Anything in the checked pattern is transparent

Mahnmut

Prime wrote: »

Pretty easy if you have a steady hand

Lasso select (from the toolbox) what you want to keep.
In the menu go Edit -> Invert Selection
Hit the delete key

Anything in the checked pattern is transparent

If this goes poorly (I don't have a steady hand), try the Magic Wand selection tool to grab the colorless background -- by default, it grabs everything of the same color as your target that's contiguous. Sort of like a fill select.

Either way, you may have to finish the process by zooming way in and blanking out left-over pixels with the eraser tool.