Thanks!
I installed this plug-in @AlphaSpace, it's working very good, I only have to test it on a black layer.
Edit: Aparrently it isn't working on a Black Layer, I think I have to change the tolerance :S
Hello, today I downloaded Paint.NET so I could make some things for my company, I made this image for my page, and I can't make it transparent for it to match my black background. Here's the image if needed.