Transparent background

[Crazy Man Dan]

In order for an image to be transparent, it must have the background color/layer removed, and it must be saved in a format that supports transparency.

If you're creating a new image, after you open Paint.NET, create a new layer and either delete the "Background" layer or set it's opacity to 0. The "Background" layer is created automatically with a white fill, so if you want transparency, you'll have to get rid of it. Then, create your image in the new layer. After you delete the "Background" layer, the background of the image should be a checkered pattern. Everything that is still checkered when you save the image will be transparent.

If you're editing an existing image, use a combination of the Magic Wand, Lasso Select, and Eraser tools to remove the part of the image you want to be transparent. When you remove that section, you should see a checkered pattern in it's place. Just as above, whatever is checkered when you save will be transparent.

When you save, you'll have to save in either a .png or .tif format. As of v2.1, Paint.NET doesn't support .gif transparency, but that feature is on the possible list for v2.2. Once that support is included, you can save as a .gif for transparency as well.